I have Van Morrison and Van Morrison & the Chieftains showing in my library as two separate artists. If you want them to appear that way, I would tag the “Irish Heartbeat” album with both the Album Artist and Track Artist as “Van Morrison and the Chieftains” You might have to Plex Dance the collaboration album to get it to show up as a new separate artist in your library.
I usually use MusicBrainz Picard for tagging, but I’m attaching screen shots from MP3Tag to show how I have them tagged.
It doesn’t properly address @beckfield 's concern, but the extended tag editor in MP3Tag shows both The Chieftains and Van Morrison as individual artists. There’s always the chance that Plex will address some of the music database shortcomings, and we won’t have to use this type of work-around (if this is one)
