Selecting to create a backup at the book level?

[FizzyWater]

I know that there's a global setting to have calibre create a backup "_original" copy of the ePub when doing an ePub-to-ePub conversion. I turned it off because I didn't necessarily want future conversions to keep using that "original" file.

However, I'm finding - when I try to use the CSS addition of "*{font-family: sans-serif;}" to switch to a san-serif font - certain of the ebooks (and it seems to be certain publishers and/or created after certain dates) will only convert the italic words to san-serif.

Is there a way in the conversion script (or maybe this is a suggestion?) to select at the time of conversion to create a backup? Once I'm comfortable that it's usually only a particular publisher, as an example, I could choose to make a backup at conversion, in case the CSS fails.