At the moment you can only see approx 30 songs (when scrolling) from a given playlist, even when you are parked. Google Music allows you to see all of your playlist when you are parked.
You can see all of your playlists when parked, surely you should be able to see the whole queue if parked?
Hey there!
While we're working with Google and employing their guidelines, we might be able to look into the amount of visible tracks.
To gauge user interest, you can post your idea to show more tracks here.