Yo,
For those of us with large nested documents, it’d be awesome if the header ‘stuck’ to the top of the screen when we were scrolling down for quick and easy access!
Either that, or a fourth area (alongside tags/bookmarks) with an easily accessible outline area. I prefer the first option though. 
Right now, if we’ve taken a new note at the bottom of our document and want to navigate (within the same document) elsewhere, we’d need to manually scroll back to the top each time!
Hope this makes sense 
Cheeers.