The RadTreeView doesn't support this scenario out of the box, but you can achieve your requirement with custom implementation. As in this case the drop functionality doesn't work you can subscribe the tree for the Drop event of the DragDropManager
and implement the drop in its handler.
For your convenience I prepared a sample project that demonstrates this approach. Keep in mind that the project is not well tested and I cannot guarantee you that it will work in all possible cases. This is why I recommend you to test and modify it in order to fit in your scenario.
Please give the project a try and let me know if it helps.
Check out Telerik Analytics, the service which allows developers to discover app usage patterns, analyze user data, log exceptions, solve problems and profile application performance at run time. Watch the videos
and start improving your app based on facts, not hunches.