When you create a new Model Driven App today, you will find that you have an options between the Modern app designer and the Classic app designer.

Existing model driven apps
Table of Contents
Today as I wanted to edit an existing app, I was presented with the Modern app designer. Which is quite confusing at first.
In the screenshot below you can see (from left to right)
- Power Automate /Power Apps navigation
- Model Driven app Designer navigation
- Model Driven App Pages/Navigation/Data navigation
- App Preview screen

As we are all used to the classic experience, this new experience will be something to get used to.
Classic app designer
In the past we used the following Classic app designer experience where we were able to edit the Site Map, Dashboard, Business Processes and the Entities within our app.

I’ve always found this UI really clunky, so I’m looking forward to the new experience.
Modern app designer
Within the modern experience we can get to the Tables in the Pages section. Then for each Table you can look at the forms and the views

This is also where you can edit your forms and your views.

When you want to update the site map, now called navigation, you only have to select the Navigation option. And you can add the Groups and Subareas as we were used to.

then the final part sits within the Data section.

This is where you can update Tables in your app and tables within your environment. In general you will want to edit the Tables in your app only.
Editing a Table will get you back to the same place as before.

Then Dashboards, they have been hidden a bit under the new page option in the Data section. But they still work in a similar way to before.

So that covers the new modern app designer.
Just one thing missing. Where are the Business Process Flows? This is one of the reasons why there is a Switch to classic mode in the top navigation of the Modern app designer.