Admin overview of filtered pages (flex objects)

We use grav with mainly protected pages (access: site.login: true) .
We miss an overview of all pages in admin which don’t have this header and thus are public accessible.

Currently there are filters for different page attributes but not for “access”.

Is there a guide to build a simple plugin that adds an admin menu entry and provides a list of all pages filtered?

If tried this but struggled to take the pages as collection but providing a different list:

I’m also unsure about connecting routes defined in the blueprint and a “Controller” provided by a plugin. Are there some resources for this?