As someone who has a lot of playlists on Spotify, and playlists of different genres, artists, etc., I thought it would be a great idea to simply add a feature to create folders for your playlists.
For example, you have these individual playlists -
With playlist folders, you could then create 2 folders called "Rap" and "Metal", which would lead to easier organization. Ex:
You could then, in theory, have the ability to expand and collapse these playlist folders, thus revealing or hiding the playlists in each folder.
Thanks for reading, and I hope this feature is added some time in the future!
Updated on 2019-08-13
This idea has already been implemented.
Find more info about playlist folders here.