I suggest adding a “like” button to the expanded notification wigdet in status bar (similarly to waht Spotify has).
This will help adding thacks to favorites quicky without a need to open the app, possibly even from the lockscreen.
A common use case is when there’s a new album added to the library, you listen to it for the first time and wish to quickly add a track you like.
Another case is when there’s a huge library imported, you shuffle the tracks and add them to favs as you go.