[Upfront Builder] upfront builder child starter theme

I want to create a child theme using the builder. I also want to use the Luke and Sara theme as a starter to work off of that design.

When I rename the theme in the builder is shows there is a conflict because the name in the directory is different than the name I gave the theme and this will cause problems with future updates.

How do I work off of an existing Upfront theme and still rename the theme to what I want it to be called?