Hello Jaromin,
Do you need a list of the opened RadWindow's objects (e.g. code) or some visual presentation of the opened windows?
If you need to get the list of all RadWindows in client code, you could use the get_windows() method:
If you need a visual representation, you could check
our MDI demo where we use RadTabStrip along with the RadWindow control.
All the best,
Georgi Tunev
the Telerik team