Screen.kt

@Composable
fun Screen() {
    // I have a state in both Screen and MySwitch.
    var checked by remember { mutableStateOf(false) }
    Row {
        MySwitch(initialChecked = false, onCheckChanged = {checked = it})
        Text(
            text = if(checked) "on" else "false",
            Modifier.clickable {
                checked = !checked
            }
        )
    }
}

@Composable
fun MySwitch(initialChecked: Boolean, onCheckChanged: (Boolean) -> Unit) {
    // I have a state in both Screen and MySwitch.
    var checked by remember { mutableStateOf(initialChecked) }
    Switch(
        checked = checked,
        onCheckedChange = {
            checked = it
            onCheckChanged(it)
        }
    )
}