This scenario cannot be achieved with the classic RadDock, since the RadWindow (Classic) cannot be added to a DockableObject (i.e. the Window will not appear like it resides within the dock). You could try using a DockableObject placed within a DockingZone, and the zone itself placed in the first DockableObject, but the inner dock has to be pinned (should not be moved) because nested docks are not supported by the RadDock for ASP.NET CLASSIC.
This, however, can be easily implemented using the RadDock for ASP.NET AJAX, by placing a DockZone inside the first dock, and then dynamically creating another dock on Button.Click and placing it into the DockZone.
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