Collections tag: Where is the counterpart in the m4b tags?

[MichA-B]

Server Version#: 4.66.1
Player Version#: several devices

Short version:
(It is related to Audiobooks/Music.)
Does anybody know which tag in m4b-files could fill the “collections tag” in Plex? (Found when editing an audiobook under “Tags”: Last thing you can edit is “Collections”.)

Background why I would like to know:
I had to reinstall my Mac. Therefore I backed up plex like a few times before. But after installing it (several times) it isn’t working as it should: Prologue is showing just a small fraction of files and plex is constantly deleting one file (always the same) every time I press “read media library files” (sorry if this not the exact term, I am using the German version). And the console is prompting a corrupt line in the database. (Already tried to repair it like described in the plex help files.)

After 3 days reading and trying several things it’s enough. I am thinking about making a new library from scratch. Therefore I have to use tags from within the m4b files. And one is missing: The collections tag.
It is important, because I am grouping the genres in Prologue with this tag, As you can see here:

If it is possible to provide plex the content of this tag from within the m4b file, I could restore the Library as often as I would like without re-entering additional data for every entry. (4500 entries in total right now.)

[certuna]

“Collections” only exist in the internal Plex database, you cannot import them from tags.

[MichA-B]

Ok, thank you very much for the answer.

[tom80H]

You actually can import them from embedded tags… however this seems to be working only for video based libraries, using the Album tag… given that’s pretty much locked for its original purpose with music/audio, this doesn’t work for those libraries.