Drag and drop from sub-window to parent

Is there any way to drag an item out of a sub-window into some component in it’s parent?

I have a GUI that has a main UI on the left, with a subwindow (in non-modal mode) on the right. I search for lists of items on the right and then I want to be able to drag the components I like from the right into a component in the parent on the left. I can drag and drop between different components seemingly fine within the same window, but when it comes to trying from a different window nothing seems to get fired.

The elements I am trying to drag out are wrapped in a DragAndDropWrapper, and the place I am dragging to implements DropHandler.