Sort by "Unused Tracks" that aren't in playlists/ haven't been exported to USB

When sorting a large library it is easy for tracks to fall through the cracks. Would be nice to have a built in feature to show when a track hasn't been sorted into a playlist. 

Another level would be to show what tracks had not been synced to any USB that was plugged in at a given moment. 

Lastly a modification to the date added column on a USB, that showed when that track was added to the USB versus to the rekordbox console itself.