Thank you for your interest in our RadNavigationView control for WPF.
At this moment of writing, the control does not support drag-drop behavior out of the box. However, you can implement drag-drop functionality using our DragDropManager. You can check the Drag-drop between GridView and TreeView help article which demonstrates how you can add such functionality to the RadGridView and RadTreeView control. You can use the code for the RadTreeView and modify it to fit for RadNavigationView. For your convenience, I have created a sample project to demonstrate this. You can check it out and extend the functionality as per your requirement. Keep in mind that the custom drag-drop behavior in the attached project does not ItemsSource property but you can modify it to respect it. I think the project will be a good starting point.