I cannot answer your first question, but for your second one: I just stumbled upon BackHandler. I just tried it real quick and it got called instead of closing the app, so that should solve your issue.

I finally started using Compose for Android and I am currently stuck at navigation. I have two questions:

1.
I have implemented a bottom navigation with three buttons and one of the buttons triggeres a nested navigation graph, like:

 HOME  ---  CONTACTS  ---  FAVOURITES 
   |            
DETAILS 

So when I open details screen from home and switch tabs, the behavior is correct, the state and last destination in the nested graph is memorized and when I tap again on home, it keeps the state and switches back to details. However, if I am on any of the other tabs and press back, it brings me to home but it resets the state, it doesn’t bring me back into details. How can I achieve that?

Navigation Bar:

@Composable
fun BottomNavigationBar(navController: NavHostController) {
BottomNavigation {
    val backStackEntry by navController.currentBackStackEntryAsState()
    val currentRoute = backStackEntry?.destination?.route

    BottomNavigationCollection.items.forEach { navItem ->
        BottomNavigationItem(
            selected = currentRoute == navItem.route,
            onClick = {
                navController.navigate(navItem.route) {
                    popUpTo(navController.graph.findStartDestination().id) {
                        saveState = true
                    }
                    launchSingleTop = true
                    restoreState = true
                }
            },
            icon = {
                Icon(
                    imageVector = navItem.icon,
                    contentDescription = navItem.title
                )
            },
            label = {
                Text(text = navItem.title)
            },
        )
    }
}

Navigation Host:

@Composable
fun NavigationHost(navController: NavHostController) {
NavHost(
    navController = navController,
    startDestination = NavigationRoutes.Home.route,
    route = "root"
) {
    homeGraph(navController)

    composable(NavigationRoutes.Contacts.route) {
        ContactsScreen()
    }

    composable(NavigationRoutes.Favorites.route) {
        FavouritesScreen()
    }
}

}

Nested Home Navigation Graph:

fun NavGraphBuilder.homeGraph(navController: NavController) {
navigation(
    startDestination = NavigationRoutes.Dashboard.route,
    route = NavigationRoutes.Home.route
) {
    composable(NavigationRoutes.Dashboard.route) {
        DashboardScreen(navController)
    }

    composable(NavigationRoutes.Details.route) {
        DetailsScreen(navController)
    }
}

}

2.
When I am back in home with the entire navigation stack clear and press back once more, naturally the app closes. How can I intercept back press and implement a “tap again to exit” confirmation feature at that point?