Best way to tag compilations (play:sub)

I just started using subsonic on my unraid server, I just bought a new truck and was looking for a way to stream music to the Apple CarPlay.
I tried play:sub looks perfect - a good proportion of the compilations on the server aren't grouped together together in albums. These are in a folder called "compilations" - the grouped compilations are in a folder "various artists" even tho' they aren't tagged, the album artist is left blank.
I use Swinsian on a Mac to play Flac files locally, which handles the tagging - It usually does a decent job, moving files to the "various artists" file, but often needs a nudge.
I checked the files in mp3tag and the compilation box is tagged, but the compilations aren't grouped together in album.
What is the best way to tag these, so I can play the compilations continuously.
I tried play:sub looks perfect - a good proportion of the compilations on the server aren't grouped together together in albums. These are in a folder called "compilations" - the grouped compilations are in a folder "various artists" even tho' they aren't tagged, the album artist is left blank.
I use Swinsian on a Mac to play Flac files locally, which handles the tagging - It usually does a decent job, moving files to the "various artists" file, but often needs a nudge.
I checked the files in mp3tag and the compilation box is tagged, but the compilations aren't grouped together in album.
What is the best way to tag these, so I can play the compilations continuously.