Putting a page or block on a whiteboard gives a choice between fully collapsed (contents invisible) and fully expanded (contents so big and scroll).
What about showing only the top-level blocks (or first children blocks)? Then I could see some of what’s inside without all the details.
I can manually do this by collapsing all of the top-level blocks in each page. But when I’m viewing the whole page, maybe I want those blocks expanded.
Concretely: a view of a block could have an attribute of how many levels deep to show. Then any view (page, embed tag, etc.) could zoom in/out.
A complexity: what if the user hits tab to create a new child at a level deeper than the view? The analogous situation with existing collapsed blocks is to change the view so that the children are visible. A simpler solution could be to immediately zoom on block parent.