Spotify Improvements
Before your click on a public playlist it should indicate to you whether or not you are already following it, which it currently does not. When you click into the playlist then you are able to see on the left that you’ve added the playlist to your library with the heart button, however if you want to go through a large list of playlists it is easy to get lost and lose track of where you started in the first place
On the desktop app in the music controller at the bottom you should be able to ad the currently playing song to any playlist with the more button or some specific add to playlist button but there is no button available to do so, you must navigate to find the track where ever it is playing deep inside some playlist. It can be annoying and time consuming if you are listening to any reasonably large playlist.