Reading the Docs would have solved this issue for you, or even kept it from happening if read before you did this
To copy a design file to be a new project just do a “save as” when you have the project open, and give the project a different name in the save dialog window. Simple as can be
You can also take benefit of the new custom templates. Add your a.design as custom template. Next time you make a new design you can use your a.design as template with all your custom settings