//Works fine, although it is no very smooth
Listener(
  child: draggable,
  onPointerMove: (PointerMoveEvent event) {
    if (event.position.dy > MediaQuery.of(context).size.height - 100) {
      // 120 is height of your draggable.
      scrollController.scrollTo(scrollcontroller.offset + 120);
    }
  },
);