Just wondering, is it considered normal that I can't set a page to be a child of a page that is hidden from the menus? I have some static pages that I'd like to stash out of the way and have it at the bottom of the list of pages. I have to unhide the parent and then rehide it after setting up the new static page, extra steps. It's only inconvenient while I'm setting up the site, I guess. No real benefit to restricting that list, I know those pages are there!
Instead of hiding the page set the view roles to only allow Admins then when you are ready to publish it set the View Roles back to All Users. This way the pages only appear in the menu for users signed in in admins role. There are reasons why it is better to not allow using pages that are not included in the menu as parent pages for other pages. Another benefit of using the view roles rather than include in menu setting for controlling publishing is that the content cannot be found in site search by non-admins if it is protected by roles whereas a page that is not included in the menu can still appear in search results if it is not protected by roles.
Hope it helps,