On the PlexAmp app you can open the library and scroll down to to “Compilations”, when I do this not all of the Compilations I have one my server are listed.
Using the Plex desktop and choosing to edit an Album there is nothing I can find to list an album as a Compilation. Also on the albums that are listed as Compilations there is nothing indicating this.
Is there a way to edit the albums to list them as Compilations?
There’s actually 2 separate things going on when it comes to compilations.
Plex will display a category for compilations that lists albums with Album Artist set to Various Artists.
Plex is using metadata from musicbrainz.org to categorize releases, e.g. albums, soundtrack, singles/eps, remixes… and compilations. You currently cannot change that categorization inside Plex (though a lot of users have started doing some clean-up on musicbrainz… with all their reviews of those changes that can take some time to tickle down into Plex).
There’s a feature suggestion asking to add an option to override the musicbrainz release type category → Music Release Type - Manual Edit - #6 by mr_mustard