I have suggested this in the past but it didn't seem to gain traction so I thought that I would bring the idea up again. It is just a very annoying feature that could be correct rather easily I would imagine. It would be nice if Canvas froze everything but the interior page. In other words, let's say you are in the "Modules" page. When you scroll down, the way it is now everything scrolls and you lose site of your courses, grades, calendar, etc. as well as all of your global settings. Depending on how long your "Modules" page is, for example, you even lose sight of the left hand navigation tabs as well (Home, Assignments, etc.) I think that those should be stationary, just as if you were to lock columns or rows in Excel.
Please also refer to this closely related idea: Make Course Menu Sticky