Plan

Premium

Device

Applies to all devices 

Operating System

All OSes. 

My Question or Issue
I'm one of the power users I suppose -- I love 'Discover Weekly'and the 'Discover' to find music. When I find good songs, I add them to Playlists. If I'm adding a song to the same playlist twice, Spotify shows me the duplicate warning. But no way to find if I'm adding a song to Playlist 2 that I already have in Playlist 1. To enableme to identify that a given song is in *any of the playlists* I've been using the "Library" (the plus sign) function. This turns into a green tick when I add it. Other than this, I have no use for the library or the 'daily mixes' etc, because I sort and shuffle my music according to my tastes. 

The issue now is this: my Library is apparently "full". Searching for help I find this is some random 'feature' from Spotify that caps this at 9999 songs or some silly thing like that. I'm totally fine with Library being as useless as it is especially with that cap.

All I'm seeking is:
To know that a song I'm listening to is in *one of my* playlists. As in: to somehow visually identify that I've added it to my self-managed repertoire of music according to my categories of taste, not by genre etc. Instead of adding it to all playlists one by one and seeing if the duplicate alert pops up...which would be a moronic way to do this basic music management task. 

How can I do this? Many thanks for any pointers.