Thank you for writing.
Drag and drop between treeviews by using the AllowDragDrop property is supported in unbound mode only. If you want to perform such in bound mode as well (or in mixed mode as in your case) you will have to implement you own drag and drop functionality. Attached you can find a sample demonstrating how this can be achieved. Feel free to modify it to match your needs.
I hope that you find this information useful.
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