Thanks for writing.
RadTreeView already has indications about which node you are dragging and on which node you are dropping. I have attached a screenshot to illustrate.
There is also the DropFeedbackColor property that sets the color of the drop line. You can set it to something more obvious, like Color.Red for example.
I hope this is what you are looking for. Please write back if you need further assistance.
the Telerik team
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