The current project I am working on requires tree to tree Drag n Drop (DnD). The Studio provides DraggableTree but it only provides DnD within the same tree: useful, but I really need tree to tree.
So I went looking for some how-to code and the Dojo Toolkit provided a solution, but as we all know, it's not simple cut n paste into your WM project. After about a day's worth of inching my way closer to a solution, I finally figured it out.
The attached project uses two HTML widgets with some div tags that define the tree that will eventually populate the HTML's real estate. The code in the Main page uses hard-coded data to populate the trees using a data store and a tree model. A bit complex for the average WM app jockey out there, but hopefully this will provide a template for you to use if you need tree to tree DnD.
By the way, this can also be a list to tree DnD or whatever two data container widgets you wish to implement. You just need to figure out the store/model implementations for the desired widget. Dojo Toolkit should be able to show you the way.