MainContent.kt

@Composable
fun MainContent() {
    Scaffold { paddingValues ->
        // ....
        val layoutDirection = LocalLayoutDirection.current
        Box(
            modifier = Modifier
                .fillMaxSize()
                .padding(
                    start = paddingValues.calculateStartPadding(layoutDirection),
                    end = paddingValues.calculateEndPadding(layoutDirection),
                    bottom = paddingValues.calculateBottomPadding(),
                )
        ) {
            Column(
                modifier = Modifier.fillMaxSize()
            ) {
                Spacer(
                    modifier = Modifier
                        .windowInsetsTopHeight(WindowInsets.statusBars)
                        .fillMaxWidth()
                        .background(Color.Red)
                )
            }
        }
    }
}