Hi,
I have just started development for a full-page app in freshsale, this app doesn’t work under the open model concept. it directly shows its data with the click of the app button itself.
Just sharing the manifest code alone to make sure the app belongs to freshsale.
The area highlighted in your screenshot if part of the product UI & you won’t be able to add any content over there. You’ll have control only within your full page app viewport. You can add a title may be centered/left aligned inside of your container itself.