I'm not sure this is really needed. It's really easy to go back to the main list of any tab - just swipe right on the list to go back (You can also tap the left arrow in the floating toolbar). You can swipe left to go back to viewing the list of songs. You don't have to drag down the Windows title bar and click the back button. If you really want arrows to advance through the main list while viewing songs, I'd need to add those in the floating toolbar at the bottom right. I can't add them in the blue header as that doesn't show up in portrait orientation. I'd prefer not to add two more icons though, as it will grow the size of that toolbar which is already fairly large.
Mike
Mike