Would be nice to be able to use a guide layer in AE outside of the composition preview window. It would be nice to have it full scale and placed off to the left of the canvas at a 1:1 ratio to the actual asset you're working on. I'm finding when doing short form edits inside of AE, I use a guide layer to make sure my cuts are on time, but also to reference creative from a previous round of work, and being able to see my guide layer without having to shy it on/off would be super useful.