[ceridwen]

Originally Posted by ilovejedd

If you know python, you can always write your own plugin.
https://manual.calibre-ebook.com/creating_plugins.html

I do know Python so yes, I can write a Calibre plugin if it's the best way to do it.

Originally Posted by ilovejedd

Note, I believe you can also use FanFicFare to download AO3 metadata and do the filtering via its personal.ini file.

I looked at this. For my uses, there are two problems: I'm dealing with metadata from sources that FanFicFare doesn't cover, and FanFicFare's metadata handling is too manual for what I want from it. One of the obvious ways to reduce the number of collections for my particular library is to exclude tags with only one example from being made into a collection. I don't think FanFicFare can do this without my modifying it pretty heavily. I'm still considering using it as one part of my toolchain.

Originally Posted by ilovejedd

Calibre is also capable of importing custom column data from the EPUB's OPF file (assuming custom column exists in the library and uses correct type and format) so another approach is to edit the OPF files inside the EPUB to add custom columns populated with your data in case you're writing in a different language.

That sounds like what I need. Does it do this automatically for any custom column?