I have been thinking about the following for a while now, what are you thoughts on it?

# Flat toggleable list for elaboration

I have always thought about a mathematical proof that works like a collapse list. When you first open it, everything is collapsed and you see the big picture, the general structure of the proofs with the biggest lemmas. Then you can expand them as needed. Wouldn't this be cool?

Use screen real estate better. Middle for main content, right side for any comment on a single line of calculation, left side for notes on one section of a proof (top left), and any theorems being used in the visible area is automatically popped into place on the left.