Looking for a way to add sub/child pages

I am looking for a way to add subpages.
I carefully read this documentation about URLs and routing: https://ghost.org/docs/api/v3/handlebars-themes/routing/
First it seemed, I could use the collections, but I got stuck on how to implement the navigation. Collections also work only with posts and not pages. It’s basically the same, but having pages would be easier to manage with a lot of posts.

I don’t want to hardcode everything, the amounts and names of the pages need to be editable from the admin interface. So I need a way to generate a navigation with a second level based on tags that pages have.

Has anybody already tried something like this?
In other CMSs it is normally a built in functionality to just assign a parent to a page and create a multi-level navigation.

I use the latest version of Ghost, self hosted on latest Debian LTS.