How can I control the duration of AnimatedVisibility in compose?

Here is an example taken from codelabs. You can add your own animation specs with the durationMillis of each animation, one for entering, and one for exiting:

 AnimatedVisibility(
    visible = shown,
    enter = slideInVertically(
        // Enters by sliding down from offset -fullHeight to 0.
        initialOffsetY = { fullHeight -> -fullHeight },
        animationSpec = tween(durationMillis = 150, easing = LinearOutSlowInEasing)
    ),
    exit = slideOutVertically(
        // Exits by sliding up from offset 0 to -fullHeight.
        targetOffsetY = { fullHeight -> -fullHeight },
        animationSpec = tween(durationMillis = 250, easing = FastOutLinearInEasing)
    )
) {
    Surface(
        modifier = Modifier.fillMaxWidth(),
        color = MaterialTheme.colors.secondary,
        elevation = 4.dp
    ) {
        Text(
            text = stringResource(R.string.edit_message),
            modifier = Modifier.padding(16.dp)
        )
    }
}

Well this is one way

@OptIn(ExperimentalAnimationApi::class)
@Composable
fun AnimatedVisibilityMark2(content: @Composable () -> Unit, visible: Boolean, durationMillis: Int) {
    AnimatedVisibility(
        visible = visible,
        enter = fadeIn(
            animationSpec = keyframes {
                this.durationMillis = durationMillis
            }
        ),
        exit = fadeOut(
            animationSpec = keyframes {
                this.durationMillis = durationMillis
            }
        )
    ){
        content()
    }
}