It seems like it would be fairly simple to add a scrollbar... I'm using a laptop so I don't know off the top of my head if MuseScore supports mouse wheels for scrolling, but it's a pain on a laptop to have to hit 'n' drag numerous times to check back at the top of the song, drag all the way back down (or try and hit the right place on the view screen near the bottom), and hit 'n' again to be able to put in notes.
If there's an easier way on laptops, please let me know. It's probably a moron error.
(My laptop uses a trackpoint by the way)