I have a structure like that:
Scaffold -> Box -> ModalBottomSheet -> Some content stuff + Button

The idea is that when I open ModalBottomSheet both in half and full state, my Button stays in the same place – at the bottom of BottomSheet (like on the pic below).

However, I have zero ideas on how to do it. If I place a button inside a nested Box, it obviously doesn’t stand still, but rolls around with it. Please help me with how I should implement this.

Fun code:

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun BottomSheetExample() {
    val coroutineScope = rememberCoroutineScope()
    val sheetState = rememberModalBottomSheetState(
        initialValue = ModalBottomSheetValue.Hidden
    )
    val openSheet = remember { mutableStateOf(false) }

    Scaffold { paddingValues ->
        Box(modifier = Modifier
            .fillMaxSize()
            .padding(paddingValues),
            contentAlignment = Alignment.Center
        ) {
            Button(onClick = { openSheet.value = true }) {
                Text(text = "Open Bottom Sheet")
            }

            if (openSheet.value) {
                ModalBottomSheet(
                    onDismissRequest = { openSheet.value = false },
                    shape = SquircleShape(32.dp, 32.dp, 0.dp, 0.dp, cornerSmoothing = CornerSmoothing.Medium),
                    containerColor = Color.White,
                    content = {
                        Box(
                            modifier = Modifier
                                .heightIn(min = 0.dp, max = LocalConfiguration.current.screenHeightDp.dp - 90.dp
                                )
                                .fillMaxSize()
                                .padding(16.dp)
                                .background(Color.LightGray)
                        ) {
                            Text(
                                modifier = Modifier.align(Alignment.TopCenter),
                                text = "This is the bottom sheet")
                        }
                    }
                )
            }
        }
    }
}

@Composable
fun rememberModalBottomSheetState(
    initialValue: ModalBottomSheetValue
) = remember {
    ModalBottomSheetState(initialValue = initialValue)
}

data class ModalBottomSheetState(
    val initialValue: ModalBottomSheetValue
)

enum class ModalBottomSheetValue {
    Hidden, Expanded
}