I've been experimenting with Upfront Builder as I'm leaning more towards creating my own themes from "scratch". In this one case, I wanted to "piggy-back" off of the SPIRIT theme and then just modify some of the elements on the homepage, contact page, about, etc. I created the new theme in builder within my primary wordpress account (www.iconmarketing.works.) I did this by creating a duplicate of the "uf-spirit" theme folder and renaming it "uf-insite" in the file manager. I modified the style.css folder and saved it.
You can see the new "insite-imw" theme that I created by duplicating the "Spirit" theme folder and renaming it in my hosting file manager.
I modified the style.css within the new "uf-insite" theme folder.
I exported the theme and installed on a subdomain called insite.iconmarketing.works. However, what I see in builder for my theme homepage is not the same once I've exported and activated on insite.iconmarketing.works.
This is what I see in Builder.