What I did was copy the Playlist Link by right clicking the playlist you want to add and navigating to the share option. After that I pasted the link into the search bar where you would essentialy add the playlist you're looking for to your Artist Profile. For some reason manually searching doesn't work but by providing the URL it did. Being brutally specific can sometimes work out!
How in the world is this still an issue? This goes back to 2016?!? Mac OS and iOS, both up to date, no scroll bar of any kind in the fly-out menu. Closing and restarting did eventually bump the play list I wanted to the top, but still no scroll bar. How can a major music ap like this still have such basic problems? I've seen numerous other issues either falsely claimed as fixed, or closed because of multiple threads but not merging them, so the threads never get enough posts on it to be deemed important enough to fix. I've long resisted using Apple's similar service, but seriously, Spotify is so thunderously clueless I've finally ponied up there.
Seriously Spotify, you need to get your stuff together.