Autoscrolling behavior is built-in, if while you move the selection the pointer is near the edge of the DiagramPanel. The margin for this behavior is controlled by Diagram.Panel.AutoScrollRegion.
However, the region is only inside the diagram. If the pointer is outside of the diagram it might be a drag-and-drop operation to a different control/window.
Ah, I didn’t recognize the feature because you need to stop drag for a while before it happens.