I have opened a ticket on GitHub, in which I present a modification respectively a proof of concept, which significantly improves the editing of pages, especially with long contents.
The save buttons are always in view with this modification, and the scroll position when editing and saving is saved and restored after saving.
You can also find a screencast and code extensions on GitHub. What do you think of that?
Link: https://github.com/processwire/processwire-requests/issues/177