Boujohn, sorry, I thought you were talking about the site menu. Then yes, unfortunately it is not possible to rearrange the order of pages as it is displayed in Control Panel. Once you have created a page as a root page or as a subpage, it stays this way in Control Panel. Though you can rearrange the pages on the site menu as you need at any time.
Also, can someone tell us what the difference in functionality there is between page and sub-page? So far it looks like it's only the placement on the Page Editor screen.
That's right, there is no actual difference in functions.
(even the Site Builder menu does not organize them in a hierarchy.)
You can organize the pages on the site menu in a hierarchy easily with drag&drop:
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