You rename a UI design as you would any other file in your project.
The .uidesign file will be highlighted.
The Project Explorer view context menu will appear.
The .uidesign file name will be editable.
The name change will take effect.
NOTE You may be warned about a need to update references to the file in the application. If a dialog appears with this warning, click the Yes button to allow the UI Designer to make the necessary updates.