You’re exactly right. As far as I know, there is no tag editing software that applies a genre to an album, the genre is applied to the individual tracks. It’s a big shortcoming when using Plex for music. Here’s one of several posts/requests to fix the problem. (Music tracks need genre)
Plex will apply the genres from the individual tracks to the album, but it requires you have the library configured to use “Prefer Local Metadata” in the advanced settings of the library. If there’s only one track in the album that has “Christmas” as a genre, the whole album will have Christmas as a genre. And that means you may get a bunch of “un-Christmas” tracks included in your playlist.
If you enable that setting, be careful, ALL of your tags need to be perfect, or you may end up with a completely broken library.
If you’re library is using genres supplied by Plex, try searching for “Holiday” as a genre…
