The flac standard-filelds are there:
A proposal for a larger list is here:
I don’t think that all these tags are relevant for FF, so there is no need to include many of them.
But since there are already suitable MP4-entries for:
TOTALDISCS and TOTALTRACKS
in the FF database anyway, these at least should be included for flac as well (although they are not flac-Standard, MP3TAG-Users might want to add them to their songs to have the same information as in their m4a-files).
I don’t know whether it is possible just to scan all the Standard field-names of, say, the MP3-, the Vorbis- and the M4A-tags (only to the extend that it is useful for the FF-database, of course) in ALL kinds of song-files. So we can be sure that most of the relevant information will be found – whatever Tag-name is used.
That would give a “next to standard”-way of including those non-standard fileds which are useful.
Thanks for all your efforts!