I think it would be nice to have the option to make the WYSIWYG editor the full height (instead of a fixed position when you open the assignment editor). Then just have the editor tools stick to the top of the page as you scroll through the assignment. This would make is so that you don't have a tiny view to work with that you have to manually resize every time by dragging. Then, Canvas would remember your assignment editor preferences and expand to full screen so that you can easily scroll the assignment to make edits with the toolbar following along as you go.