Talked to customer service. They didn't even know about the custom UI transfer. They said I'd have to re-do all of my settings and all of my key bindings. I thought they were stored on the server?
The key bindings will definitely stay. Was playing on a different computer yesterday and I had to redo all the UI customization (I didn't transfer any files or anything), but when I enabled the quick bars my key bindings were all there. And you have to redo all the other settings, too, like the subtitles and everything.