I have a ton of playlists. I would love the ability to organize these playlists into folders... or playlists of playlists. For example, I'd have one called "Exercise music" and another called "Deep Work". It'd be awesome to be able to add other people's playlists to these parent playlists. In additional to that, it'd be awesome to be able to have a customized "view" of those other people's playlists within the context of my parent playlists. That is, I want the ability to say that, "I like this other person's playlist, but I don't like this song on her playlist." So, I can filter out that one song while still benefiting from the otherwise great judgement of that other person to add more awesome tracks to her playlist which will in turn appear on my parent playlist. Unliking a track in this way should be super easy as in just clicking a button on the play bar.