showsDismissIndicator

Whether to offer the grab affordance for the drag.

Follows swipeToDismiss rather than defaulting to true, so a structural graph never promises a handle it cannot honour.

The graph being dragged is the surface the affordance belongs to, so this decides for every step taken inside it. Setting it to false leaves the graph draggable with no handle and no strip reserved above its layout, which is how a vertically presented flow keeps the gesture without the grabber.