Hello Greg Case,
First excuse me for the delay in communication.
I have prapared a sample project that demonstrates that the GridViewExpandableRow can be registered by the drag and drop manager.
There are two important configurations that should be made before the manager can register the GridViewExpandableRow for drag and GridViewRow for drag and drop.
First you should allow the drag and drop like this:
The second important thing is to set the e.QueryResult = true in the OnDropQuery and OnDragQuery query events whenever that is applicable.
After that you should get both row types as Destination in the DragInfo events.
Hope this helps.
If you have more questions do not hesitate to write.
Sincerely yours,
Milan
the Telerik team