A Customizable scrollbar that can be applied in any composable in jetpack compose that supports a Modifier. The scrollbar is not interactive and is just an indicator for the current position of the ScrollState.

ComposeScrollbar.kt

@Composable
fun Modifier.verticalScrollBar(
    state: ScrollState,
    color: Color = Color.Gray,
    ratio: Float = 3f,
    width: Dp = 8.dp,
    alwaysOn: Boolean = false
): Modifier {
    val targetAlpha = if (state.isScrollInProgress || alwaysOn) 1f else 0f
    val duration = if (state.isScrollInProgress) 150 else 500

    val alpha by animateFloatAsState(
        targetValue = targetAlpha,
        animationSpec = tween(durationMillis = duration), label = "scrollBarAlpha"
    )

    return drawWithContent {
        drawContent()

        val needDrawScrollbar = state.isScrollInProgress || alpha > 0.0f
        val barHeight = (this.size.height / ratio)
        val barRange = (this.size.height - barHeight) / state.maxValue
        if (needDrawScrollbar) {
            val position = state.value * barRange
            drawRect(
                color = color.copy(alpha = alpha),
                topLeft = Offset(this.size.width - width.toPx(), position),
                size = Size(width.toPx(), barHeight)
            )
        }
    }
}