DragDrop on TWorkflowDiagram

How to Implement the OnDragDrop on a TWorkflowDiagram.

Placing the selected TDiagramContol by different buttons.
 
The TButton.OnStartDrag does TWorkflowDiagram.StartInsertingContol

The only way for automatic bloc insert is using StartInsertinngControl, which will allow block insertion through a click or drawing a rectangle. If you want to just drag something to the diagram and create a block on drop, you must implement it yourself. It's not that hard, you just implement regular Drag/Drop operations, and then on the drop event you create a block directly in the diagram. You must of course use your own toolbar, you can't drag/drop buttons from the built-in diagram toolbar.

How to Create a TDiagramControl by Code

Take a look at this: http://www.tmssoftware.com/site/diagram.asp?s=faq&show=149