animateFloatingActionButton

@ExperimentalMaterial3ExpressiveApi
fun Modifier.animateFloatingActionButton(
    visible: Boolean,
    alignment: Alignment,
    targetScale: Float = FloatingActionButtonDefaults.ShowHideTargetScale,
    scaleAnimationSpec: AnimationSpec<Float>? = null,
    alphaAnimationSpec: AnimationSpec<Float>? = null
): Modifier

import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.rememberLazyListState
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Add
import androidx.compose.material3.FabPosition
import androidx.compose.material3.FloatingActionButton
import androidx.compose.material3.FloatingActionButtonDefaults
import androidx.compose.material3.Icon
import androidx.compose.material3.MediumFloatingActionButton
import androidx.compose.material3.PlainTooltip
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Text
import androidx.compose.material3.TooltipAnchorPosition
import androidx.compose.material3.TooltipBox
import androidx.compose.material3.TooltipDefaults
import androidx.compose.material3.animateFloatingActionButton
import androidx.compose.material3.rememberTooltipState
import androidx.compose.runtime.derivedStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp

val listState = rememberLazyListState()
// The FAB is initially shown. Upon scrolling past the first item we hide the FAB by using a
// remembered derived state to minimize unnecessary compositions.
val fabVisible by remember { derivedStateOf { listState.firstVisibleItemIndex == 0 } }

Scaffold(
    floatingActionButton = {
        // A FAB should have a tooltip associated with it.
        TooltipBox(
            positionProvider =
                TooltipDefaults.rememberTooltipPositionProvider(TooltipAnchorPosition.Above),
            tooltip = { PlainTooltip { Text("Localized description") } },
            state = rememberTooltipState(),
        ) {
            MediumFloatingActionButton(
                modifier =
                    Modifier.animateFloatingActionButton(
                        visible = fabVisible,
                        alignment = Alignment.BottomEnd,
                    ),
                onClick = { /* do something */ },
            ) {
                Icon(
                    Icons.Filled.Add,
                    contentDescription = "Localized description",
                    modifier = Modifier.size(FloatingActionButtonDefaults.MediumIconSize),
                )
            }
        }
    },
    floatingActionButtonPosition = FabPosition.End,
) {
    LazyColumn(state = listState, modifier = Modifier.fillMaxSize()) {
        for (index in 0 until 100) {
            item { Text(text = "List item - $index", modifier = Modifier.padding(24.dp)) }
        }
    }
}