Thank you for your reply, but perhaps I wasn't clear.
I'm going to simplify my task for now. Let me refer you to your own sample:
http://www.syncfusion.com/support/kb/1737/How-can-I-use-more-than-one-DockingManager-in-my-windowsIt has two DockingManager's on the window with two ListBoxes in each. You can dock and float ListBoxes in each DockingManager, but not across. That is, you can't drag a ListBox from one DockingManager and drop it and dock it to another DockingManager. And that's exactly what I'm trying to achieve.
No, I can not use one DockingManager, since I actually need to have them on two DIFFERENT windows.
Basically, I'm looking for DockingManager.AddToTargetManagersList method that apparantely exists in Winform version of DockingManager but not in WPF version.