As a confluence-administrator I am able to remove restrictions in the "Restricted Pages" tab in any space-admin-area.
Whenever I need to admin-edit a page with edit restrictions, I'll have to remove all restrictions (i.e. allowing public edit!) in there.
After editing the page, I'll need to restore the old page restrictions.
It would be nice to allow admins to add themselves to the list. With that feature an admin would no longer be required to remove all restrictions of a page in order to edit that page.
See also the support ticket: CSP-69282