If you follow for example sleep playlist, and you do not follow 1 or 2 but 5 or more sleep playlist. I would like to put all in a folder labeled sleep instead of running down my list to find that one sleep playlist that I really want to hear on that night. I know with me I follow sometimes 5 or more playlist with the same subject, and I would love it if I could put them in folders. Instead of looking down my mile long list of subjects to just find that one playlist I want to listen to. It will be nice to have folders for all the playlist I follow. So that way I do not go up and down looking for just that one I want to listen to right now. It takes me almost an hour to find just that one playlist, and to be honest...I get so mad at not finding it that I go and do other stuff or pop in a favorite CD of mine that I CAN find.
I've got good news for you, the feature to create playlist folders is already available. You can create the folders from the desktop version of Spotify. More info on this can be found in the image below.