Currently Symfonium lets me add a single track multiple times to a same local playlist. Ability to have a playlist which will only allow unique tracks (or ignore duplicate tracks if added again) would help manage offline playlists better.
My library is moderately huge and I accidently add the same tracks to playlists. I frequently find myself deleting the duplicates. Having the ability to filter out duplicates in a playlist would be a big help
Better management of offline playlists
Other application solutions:
Youtube playlists doesn’t allow duplicates in a playlist, if we try to add a track thats already present in a playlist then it would show checkboxes for the playlists if present already