Page attribute "Parent" has no effect

We’re working on a website where multiple administrators (author role) will only be able to manage some pages and it’s subpages.
He/she can also create new pages in his section.
This is all possible using Presspermit.
We’re using the Woothemes Canvas theme.

I was expecting one can add a page to the main menu by selecting the parent page in the page attributes “Parent” dropdown.
However this does not seem to work at all.
One has to go to Appearance – menu to add the page.
First of all this seems too complicated for some basic users.
Secondly, we don’t want to give all administrators access to the Appearance – menu section.

How can we solve this?
It should be quite easy to allow selection of the parent page to automatically add the page in the custom menu?
Anyone knows of some kinde of plugin available?

Thanks for any help!

Mark