It would be really handy to be able to see the playlists in which a particular song is.
If one already has a lot of playlists which group similar songs together, it could be potentially much easier to find several kinds of similar songs.
It would fit to the other functionality in the song menu like same artist, album or genre. There it could have the same symbol as the playlists entry in the library view, and be positioned next to the "+ playlist" button.
Edit: sorry for the wrong board, can you please move it?
