Create you own

That's it. Now it's time to let show your creativity. The admin is not made to let you have a magic crud functionality or help you with anything. Just create and make something beautiful.

Just note a basic folder setup when you build a bundle or add some to the basic admin.

Controller (for site controllers)
Controller/Admin (for admin controllers, add a @Route("/admin") in the class)
Controller/Api (for api controllers, add a @Route("/api") in the class)
Resources/view (for views)

And just don't forget to have fun!