I am having a problem that seems similar to one of Andrei.
I have created an exaple project to demonstrate this.
What I try to achieve is to drag and drop an item to any other node. This means dropping a child to its direct parent or dropping a parent to its child.
In our program each node is an entry in virtual file system where this behavior is possible (and needed).
In the demo project there is one parent node, which contains two child nodes. You can simply drop on child on the other. But you cannot drop one of the child nodes to the parent node. This drop would result in copy (internally), creating a new node.
I found no event where I could enable this drop operation.