Write Page

Is there a plugin, or a known way, or even the possibility to customise the page parent meta box on the write page screen.

I am setting up a CMS style site and am anticipating an increasingly complex scrollbox with multiple pages and subpages.

What would be ideal is a collapsible menu to choose the page parent.

I know this can be done using plugins such as pagemash once the page is published, but it would be ideal to have it as an option at the time of writing.