Hey, it happened the same to me. I don’t know if this is the right way to do it, but I found an Export option in the 3 dots menu at the top-right of the editor. If you upload those files to your child theme, I think you should have the customizations you did to the main Theme.
In my case, the problem was that the header dissapeared with an error if I followed these steps. Maybe you’re luckier than me… Good luck!
