One should be able to persist to a file all changes made when using the element hierarchy editor at design time.
It will be nice if one can add his custom sub menu items at design-time through the 'Add new item' menu. This was supported in the past, but the support was removed together with the introduced design-time optimizations.
Currently the sgen tool raises an exception when executing it on RadControls and RadControls.UI. There is also an XmlSerialization exception when loading the application.