The 2 playlists should be identical in content. Basically, when a new track is dragged in the horizontal playlist, the player playlist should be updated as well (when a lot of tracks get spanned, both playlists should be updated)
Partially done, i.e. when a track is drag dropped to horizontal playlist, the bar ui playlist gets updated as well.
Still to consider observing for all events:
track removed from one of the playlists => update the other
track added to one of the playlists => update the other (regardless from where/how it gets added)
The 2 playlists should be identical in content. Basically, when a new track is dragged in the horizontal playlist, the player playlist should be updated as well (when a lot of tracks get spanned, both playlists should be updated)