@melovesflying: Is the goal to create a collecton for "Finished Books" or "Unfinished Books", or both?
EDIT: On my end, simply ticking "Create" for a tristate column does the right thing: anything with that column set to true ends up in a collection named after the human-readable name of said column.
So, basically, just set the action to Create, forget all my crappy ramblings from yesterday and leave everything else blank, and you're done

.
Code:
=== Kindle Collections 1.7.16 PREVIEW Report
Preview only - no collections have actually been modified on the Kindle.
Collections saved to the Kindle:
Collection Managed By Books Change
---------- ---------- ----- ------
Read Calibre 5 Replaced (from column Read)
Test Kindle 1 None (preserve Kindle-only is True)
No collections selected to delete from the Kindle.
=== Settings:
Column: Read
Action: Create
Prefix: ""
Suffix: ""
Minimum: ""
Ignore: ""
Include: ""
Rename from: ""
Rename to: ""
Split on: ""
Never delete/modify these Kindle collections:
Action when toolbar icon is clicked: Show menu (default)
Preserve existing Kindle-only collections: True
Ignore prefix/suffix when comparing Calibre names: True
Ignore case when pattern matching: True
Reset collection times: True
Ignore exported collections db: False
Only build a diff database: False
Kindle Model: 540
Calibre Personal doc tag: +Pdoc
Kindle collections file: /run/media/niluje/Kindle/system/collections.json
Plugin customization file: /home/niluje/.config/calibre/plugins/Kindle Collections.json
System Encoding: UTF-8
A search for
ondevice:true AND #read:true confirms that it's doing the right thing.
Note that my Read column is tristate, but that shouldn't be a factor here compared to a boolean one.