Need help? Check out Spotify Answers for solutions to a wide range of topics.
I think it would be useful if, under the "Add to playlist" option, there was an option to view which of your playlists the song already features in.
I find when exploring new music, or listening to songs I've liked, it's good to know which playlists I've already added it to, if any.
Updated on 2021-02-02
Thanks for submitting this to the Idea Exchange!
Spotify Staff will look into this idea once it reaches the necessary amount of votes.
In the meantime, it’d be great to take a look at this Idea and give it your +VOTE since it's suggesting something along the lines of what you have in mind.
More info on how your feedback reaches Spotify via the Idea Exchange can be found here.