@youtubemusic Android app is super buggy. Help & feedback spins for a while then closes when I try to use it, so here I am if you'd like to ask "OK, what else?"
The other serious issue is that often a playlist I created by doing "Add to playlist"->"Create new playlist" doesn't show up in the "My playlists" popup the next time I do "Add to playlist", so I can't add anything else. The playlist does appear in Library ->Playlists.