How do you organize spin-off movies and TV shows?

[bigggtuna]

For shows that have movie tie-ins like Bobs Burger I would put the movie in the specials folder of the show. There you can set it to play automatically after the desired show.
If you add the TVDB and TMDB plugins to your jellyfin server you can have them both as metadata sources for the show and should be able to fetch the metadata in most cases (For Bobs Burger specifically the movie is listed as a special in TVDB). In my experience it is easier to add the TMDB/TVDB/IMDB ID whilst editing the metadata of the movie in Jellyfin itself and not in the filename.

I can fiddle around with that, it didn't come to mind that different sources would have different specials, but I guess that makes sense!

Another option that is, IMO, simpler is to use playlists.

I hadn't thought of that either, but I'm not sure that adding a third different area to go looking for something to watch would make me feel better about it. Perhaps nothing will, lol.