To set the height of a Composable to a specified size, pass Modifier.height() to the modifier parameter. The unit is dp.

@Composable
fun Greeting2(name: String) {
    Column {
        Text(text = "こんにちは", 
            modifier = Modifier.height(40.dp))
        Text(text = "$name!")
    }
}

"こんにちは" text height is set to 40dp instead of content size.