This feature is badly needed! Expandable collapsable folders / groups. Heck you could even throw a little search bar at the top to help get to the page you are looking for.
This is an old post, but I just wanted to share just in case others end up here looking for an answer to this: You can collapse those panels! The key-command to do so is Command + . on a Mac, Ctrl + . on Windows.
I find that it becomes difficult to navigate through my pages when my design file has 10 - 20 pages in it. As a result, I end up creating artificial page groups with fake pages that I rename “-”.
It would be nice if there were a built-in feature that would allow me to organize my pages into groups. Does anyone else feel the same? Tried to find a plugin, but didn’t have any luck.