If you right click and ‘make a copy’ of an existing design, you can then modify using add art or delete, while the settings remain on the design already used.
This is a bit limited but it would bring your settings up in a different UI and not mess with the origin design in any way.
Thanks for the help, everyone. @brokendrum’s suggestion to make a new copy of your design file on the app Dashboard before editing the artwork is a good way to retain some settings for iterative design work.
I hope this helps, and I’ll pass on the suggestion for a “reupload” feature as you described. Please post a new thread or email us at support@glowforge.com if you run into any trouble. Happy printing!