The height of Box is 0 and I'm not sure why.

Row(modifier) {
        Box(
            modifier = Modifier
                .width(24.dp)
                .fillMaxHeight()
                .background(color = Color.Blue)
        )
        Text(modifier = Modifier.align(Alignment.CenterVertically), text = "Theme")
    }

You might need to add brackets to the end of the Box to denote empty content?

Thanks but neither of those worked. Curly braces are optional and do nothing if not added, and Weight wouldn't apply to height, because this is in a Row

What is being passed in the modifier in the parent Row?