[deback]

Here are the rules I've added to the Transform section of Look and Feel:

Spoiler:

# If the property margin-left is 30px
# Change the value to0
query: 30px
match_type: is
action_data: 0
action: change
property: margin-left

# If the property margin-right is 30px
# Change the value to0
query: 30px
match_type: is
action_data: 0
action: change
property: margin-right

# If the property text-indent is greater than .01em
# Change the value to1.2em
query: .01em
match_type: >
action_data: 1.2em
action: change
property: text-indent

# If the property word-wrap is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: word-wrap

# If the property hyphens is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: hyphens

# If the property -epub* is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -epub*

# If the property word-break is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: word-break

# If the property -moz-hyphens is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -moz-hyphens

# If the property -webkit-hyphens is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphens

# If the property adobe-hyphenate is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: adobe-hyphenate

# If the property text-indent is greater than .01%
# Change the value to1.2em
query: .01%
match_type: >
action_data: 1.2em
action: change
property: text-indent

# If the property text-indent is greater than or equal to .01px
# Change the value to1.2em
query: .01px
match_type: >=
action_data: 1.2em
action: change
property: text-indent

# If the property text-autospace is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: text-autospace

# If the property tab-stops is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: tab-stops

# If the property -aw-left-pos is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -aw-left-pos

# If the property -aw-rel-hpos is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -aw-rel-hpos

# If the property -aw-rel-vpos is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -aw-rel-vpos

# If the property -aw-wrap-type is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -aw-wrap-type

# If the property -aw-top-pos is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -aw-top-pos

# If the property -aw-bookmark-end is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -aw-bookmark-end

# If the property line-height is less than or equal to 1.2
# Change the value to1.2
query: 1.2
match_type: <=
action_data: 1.2
action: change
property: line-height

# If the property line-height is less than or equal to 1.2em
# Change the value to1.2
query: 1.2em
match_type: <=
action_data: 1.2
action: change
property: line-height

# If the property line-height is greater than or equal to 1.2em
# Change the value to1.2
query: 1.2em
match_type: >=
action_data: 1.2
action: change
property: line-height

# If the property line-height is greater than or equal to 1.2
# Change the value to1.2
query: 1.2
match_type: >=
action_data: 1.2
action: change
property: line-height

# If the property -epub-hyphens is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -epub-hyphens

# If the property -web-hyphens is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -web-hyphens

# If the property margin-top is 2 em
# Change the value to2em
query: 2 em
match_type: is
action_data: 2em
action: change
property: margin-top

# If the property margin-left is 2 em
# Change the value to1em
query: 2 em
match_type: is
action_data: 1em
action: change
property: margin-left

# If the property text-justify-trim is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: text-justify-trim

# If the property oeb-column-number is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: oeb-column-number

# If the property -webkit-text-fill-color is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-text-fill-color

# If the property box-shadow is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: box-shadow

# If the property so-language is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: so-language

# If the property punctuation-wrap is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: punctuation-wrap

# If the property letter-spacing is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: letter-spacing

# If the property adobe-text-layout is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: adobe-text-layout

# If the property -webkit-hyphenate-charactor is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphenate-charactor

# If the property -webkit-hyphenate-limit is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphenate-limit

# If the property -webkit-hyphenate-after is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphenate-after

# If the property -webkit-hyphenate-before is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphenate-before

# If the property -moz-box-sizing is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -moz-box-sizing

# If the property -o-box-sizing is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -o-box-sizing

# If the property -webkit-box-sizing is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-box-sizing

# If the property -o-hyphens is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -o-hyphens

# If the property -webkit-text-stroke is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-text-stroke

# If the property -webkit-tap-highlight is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-tap-highlight

# If the property -webkit-box-shadow is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-box-shadow

# If the property float is bottom
# Remove the property
query: bottom
match_type: is
action_data:
action: remove
property: float

# If the property page-break is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: page-break

# If the property -webkit-tap-highlight-color is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-tap-highlight-color

# If the property -ms-hyphens is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -ms-hyphens

# If the property -webkit-border-radius is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-border-radius

# If the property -webkit-hyphenate-lines is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphenate-lines

# If the property hyphenate-after is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: hyphenate-after

# If the property hyphenate-before is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: hyphenate-before

# If the property hyphenate-lines is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: hyphenate-lines

# If the property max-height is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: max-height

# If the property max-width is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: max-width

# If the property text-align is middle
# Change the value tocenter
query: middle
match_type: is
action_data: center
action: change
property: text-align

# If the property -epub-line-break is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -epub-line-break

# If the property -epub-text-align-last is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -epub-text-align-last

# If the property color is windowtext
# Remove the property
query: windowtext
match_type: is
action_data:
action: remove
property: color

# If the property epub-hyphens is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: epub-hyphens

# If the property text-align is top
# Change the value tocenter
query: top
match_type: is
action_data: center
action: change
property: text-align

# If the property text-align is bottom
# Change the value tocenter
query: bottom
match_type: is
action_data: center
action: change
property: text-align

# If the property -webkit-line-break is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-line-break

# If the property -webkit-nbsp-mode is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-nbsp-mode

# If the property -webkit-font-kerning is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-font-kerning

# If the property -webkit-hyphenate-limit-before is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphenate-limit-before

# If the property -webkit-hyphenate-limit-after is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphenate-limit-after

# If the property -webkit-hyphenate-limit-lines is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphenate-limit-lines

# If the property text-align is justified
# Change the value tojustify
query: justified
match_type: is
action_data: justify
action: change
property: text-align

# If the property -adobe-float-keep is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -adobe-float-keep

# If the property break-before is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: break-before

# If the property break-after is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: break-after

# If the property text-align is start
# Remove the property
query: start
match_type: is
action_data:
action: remove
property: text-align

# If the property transition is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: transition

# If the property -epub-ruby-position is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -epub-ruby-position

# If the property -epub-text-combine is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -epub-text-combine

# If the property -webkit-text-combine is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-text-combine

# If the property text-decoration is normal
# Remove the property
query: normal
match_type: is
action_data:
action: remove
property: text-decoration

# If the property text-align is initial
# Remove the property
query: initial
match_type: is
action_data:
action: remove
property: text-align

# If the property cellspacing is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: cellspacing

# If the property height is 98vh
# Change the value to98%
query: 98vh
match_type: is
action_data: 98%
action: change
property: height

# If the property height is 99vh
# Change the value to99%
query: 99vh
match_type: is
action_data: 99%
action: change
property: height

# If the property height is 65vh
# Change the value to65%
query: 65vh
match_type: is
action_data: 65%
action: change
property: height

# If the property -webkit-background-size is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-background-size

# If the property background-size is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: background-size

# If the property list-style-type is normal
# Remove the property
query: normal
match_type: is
action_data:
action: remove
property: list-style-type

# If the property -aw-number-format is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -aw-number-format

# If the property font-kerning is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: font-kerning

# If the property line-height is normal
# Change the value to1.2
query: normal
match_type: is
action_data: 1.2
action: change
property: line-height

# If the property -epub-word-break is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -epub-word-break

# If the property -ms-word-break is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -ms-word-break

# If the property text-align is baseline
# Remove the property
query: baseline
match_type: is
action_data:
action: remove
property: text-align

# If the property text-align is left
# Change the value tojustify
query: left
match_type: is
action_data: justify
action: change
property: text-align

# If the property -qt-block-indent is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -qt-block-indent

# If the property -qt-paragraph-type is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -qt-paragraph-type

# If the property border-bottom-width is 1
# Change the value to1px
query: 1
match_type: is
action_data: 1px
action: change
property: border-bottom-width

# If the property border-left-width is 1
# Change the value to1px
query: 1
match_type: is
action_data: 1px
action: change
property: border-left-width

# If the property border-right-width is 1
# Change the value to1px
query: 1
match_type: is
action_data: 1px
action: change
property: border-right-width

# If the property border-top-width is 1
# Change the value to1px
query: 1
match_type: is
action_data: 1px
action: change
property: border-top-width

# If the property -khtml-hyphens is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -khtml-hyphens

# If the property border-bottom-color is initial
# Remove the property
query: initial
match_type: is
action_data:
action: remove
property: border-bottom-color

# If the property border-bottom-style is initial
# Remove the property
query: initial
match_type: is
action_data:
action: remove
property: border-bottom-style

# If the property border-top-color is initial
# Remove the property
query: initial
match_type: is
action_data:
action: remove
property: border-top-color

# If the property border-top-style is initial
# Remove the property
query: initial
match_type: is
action_data:
action: remove
property: border-top-style

# If the property webkit-line-box-contain is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: webkit-line-box-contain

# If the property width is intrinsic
# Remove the property
query: intrinsic
match_type: is
action_data:
action: remove
property: width

# If the property text-align-last is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: text-align-last

# If the property -webkit-transform is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-transform

# If the property text-rendering is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: text-rendering

# If the property -webkit-line-box-contain is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-line-box-contain

# If the property -webkit-hyphenate-character is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: -webkit-hyphenate-character

# If the property font-weight is light
# Change the value tonormal
query: light
match_type: is
action_data: normal
action: change
property: font-weight

# If the property box-decoration-break is slice
# Remove the property
query: slice
match_type: is
action_data:
action: remove
property: box-decoration-break

# If the property background-color is FFFFFF
# Remove the property
query: FFFFFF
match_type: is
action_data:
action: remove
property: background-color

# If the property line-spacing is any value
# Remove the property
query:
match_type: *
action_data:
action: remove
property: line-spacing

# If the property line-height is auto
# Change the value to1.2
query: auto
match_type: is
action_data: 1.2
action: change
property: line-height

Most of these entries will remove many or most of the CSS codes that Calibre says are invalid, so they are never listed when I check the book after running the conversion--which saves a ton of time.