What is the best way to implement a TopAppBar accross multiple screen (but not all of the screens)? Do I have to implement it in each and every screen or is there a way to join several screens with a single TopAppBar. I'm working with Navigation API.

I typically have a top level bottom tab bar, and then the top app bar is setup in each screen individuallly. this is how i setup my shared bottombar: https://developer.android.com/jetpack/compose/navigation#bottom-nav I suppose if you wanted a single top app bar you can use the same sort of conditional logic to hide/show it. but some of my toolbars are pretty well integrated into the screen (like a collapsing image that collapses into a top bar) so having top bar in every screen has been the way i went in multiple apps with good results.