If you are listening to a Tidal song and add it to your playlist but not to your library it won’t show the ‘Playlists: XYZlist’ under the song. The only way to get around this is to first add it to your library then add it to your playlist.
Why this is annoying is because sometimes you might be browsing tidal albums through roon and find a good song and want to add it to your play list but maybe its already there? If it had the ‘playlists: XYZ’ under it reliably then you know you already have the song on your playlist. But if its not here you have to go back to your playlist and manually scroll through to see if its there.
Please have a look at this.