That's easy. You'd have pages and subpages displayed in a column. Pages
would be left-aligned. Subpages would be indented.
To reorder pages, you'd drag them up or down, and drop them where you wanted
them to go. To turn a page into a subpage, you'd drag it up or down, till you
found the page you wanted it to be a subpage of. Then you'd drag it to the
right, under that page.
This is much easier to do than to describe! I've done it in many other
programs. It's the way most outliners work, including the one in Microsoft
And it has other advantages. You can quickly turn a subpage into a page. You
can create many levels of subpages. Working this way is completely intuitive,
and needs very little explanatoin. By contrast, OneNote's structure of
sections, pages, subpages, and section groups takes a while to get used to.