To batch modify a CSS property
Please have a look at this working script.
https://www.mobileread.com/forums/sh...90#post3587090
I think this gives some interesting possibilities to batch modify EPUB. This task could be handled by a Calibre plugin, because Calibre has built-in batch-processing capabilities.
For example one could thus previously tweak a batch of EPUB before a Kindle conversion (some CSS properties may be incompatible for this task).
A more ambitious purpose would be to define custom stylesheets that'll be added during all Calibre conversions .I.e., it might be easier to add all epubs to Calibre, define a custom stylesheet and then do an epub-to-epub conversion.
As I am not a coder, I'll leave this idea here, hoping that somebody will pick it up.