@Composable
fun MainScreen() {
   val mainNavController = rememberNavController()
   val homeNavController = rememberNavController()
   val scaffoldState = rememberScaffoldState()

   NavHost(
      navController = mainNavController,
      startDestination = "main"
   ) {
      composable("main") {
         Box(Modifier.fillMaxSize()) {
            TextButton(
               modifier = Modifier.align(Alignment.Center),
               onClick = { mainNavController.navigate("home") }
            ) {
               Text("Home")
            }
         }
      }

      composable("home") {
         Scaffold(
            scaffoldState = scaffoldState,
            bottomBar = {
               BottomNavigation {
                  val navBackStackEntry by homeNavController.currentBackStackEntryAsState()
                  val currentDestination = navBackStackEntry?.destination

                  BottomNavigationItem(
                     icon = {
                        Icon(
                           Icons.Default.Share,
                           contentDescription = "Tab 1"
                        )
                     },
                     label = { Text("Tab 1") },
                     selected = currentDestination?.hierarchy?.any { it.route == "home/tab1" } == true,
                     onClick = {
                        homeNavController.navigate("home/tab1") {
                           popUpTo(homeNavController.graph.findStartDestination().id) {
                              saveState = true
                           }
                           launchSingleTop = true
                           restoreState = true
                        }
                     }
                  )

                  BottomNavigationItem(
                     icon = {
                        Icon(
                           <http://Icons.Default.Menu|Icons.Default.Menu>,
                           contentDescription = "Tab 2"
                        )
                     },
                     label = { Text("Tab 1") },
                     selected = currentDestination?.hierarchy?.any { it.route == "home/tab2" } == true,
                     onClick = {
                        homeNavController.navigate("home/tab2") {
                           popUpTo(homeNavController.graph.findStartDestination().id) {
                              saveState = true
                           }
                           launchSingleTop = true
                           restoreState = true
                        }
                     }
                  )
               }
            }
         ) {
            NavHost(
               navController = homeNavController,
               startDestination = "home/tab1"
            ) {
               composable("home/tab1") {
                  Box(
                     Modifier
                        .fillMaxSize()) {
                     Column( modifier = Modifier.align(Alignment.Center)) {

                        Text("Tab 1")

                        TextButton(
                           onClick = {
                              mainNavController.navigate("main")
                              homeNavController.navigate("home/tab1")
                           })
                        {
                           Text("Main")
                        }
                     }
                  }
               }
               composable("home/tab2") {
                  Box(
                     modifier = Modifier.fillMaxSize(),
                  ) {
                     Column( modifier = Modifier.align(Alignment.Center)) {

                        Text("Tab 2")

                        TextButton(
                           onClick = {
                              mainNavController.navigate("main")
                           })
                        {
                           Text("Main")
                        }
                     }
                  }
               }
            }
         }
      }
   }
}

You still need to figure out what needs to go inside and outside that level, whether you are using Navigation Compose or not

fun MainScreen() {
   val bottomSheetNavigator = rememberBottomSheetNavigator()
   val navController = rememberNavController(bottomSheetNavigator)

   NavHost(
      navController = navController,
      startDestination = "main"
   ) {
      homeGraph(navController, bottomSheetNavigator)

fun NavGraphBuilder.homeGraph(
   navController: NavController,
   bottomSheetNavigator: BottomSheetNavigator
) {
   composable("home") {
      val scaffoldState = rememberScaffoldState()

      ModalBottomSheetLayout(bottomSheetNavigator) {
        Scaffold(
            scaffoldState = scaffoldState,
            drawerContent = {...},
            bottomBar = {...}
        ) {
            // Not entirely sure how to setup bottom nav tabs within the scaffold?
        }
      }
  }
}

Dialog

ModalBottomSheetLayout

composable

fun NavGraphBuilder.bottomNavWrappedComposable(
  navController: NavController,
  // all the normal parameters to composable including the content block:
  content: @Composable (NavBackStackEntry) -> Unit
) = composable(
  // Add in all of the normal parameters
) { entry ->
  // Scaffold uses an expensive SubcomposeLayout, you really just need a Column
  Column {
    // First, display the content in a Box
    Box(modifier = Modifier.weight(1f) {
      content(entry)
    }
    // Then put your BottomNavigationBar, using the same logic as
    // the docs use: <https://developer.android.com/jetpack/compose/navigation#bottom-nav>
    BottomNavigationBar(
      // This would be the secret sauce that would keep the bottom bar in place as
      // other elements transition as you move between screens
      modifier = Modifier.sharedElement("bottomBar")
    ) {
      // your items
    }
  }
}