Adding sections in the 'Pages' post type

I'm wondering if there is a way to add titles or nested groups to the pages post type. A website of ours have an enormous amount of pages so we want to order the pages in (preferably) groups/categories without changing the permalink structure.

Now:

- Page 1
- Page 2
- Page 3

to:

Normal pages:
 - Page 1

Landing pages:
 - Page 2
 - Page 3

I can't find a plugin or a way to develop this into the WP backend.

Any help would be greatly appreciated!