Thank you for writing.
The easiest way to achieve the desired behavior is to set the CloseAction
of the ToolWindow to Hide.
When the user would like to reopen the window, you can simply .Show()
the ToolWindow instead of create a new instance. RadDock keeps the position of its hidden windows, so the ToolWindow will automatically appear exactly in the location it was closed.
I hope you find my answer useful. Let me know if you have further questions.
the Telerik team