How to show page hierarchy tree on top of the page content

You mean like breadcrumbs show it?

Hi there,

By default WordPress doesn't allow categories on static pages so I'm not sure how this would work?

yes sir

Not sure if I understand.

Have you added categories to pages?

Leo is correct static pages have "your homepage as a parent", nothing you can do to add to them a different path!
https://wordpress.com/support/post-vs-page/