I’ve got the same issue: I want to move from a v1 theme over to v2 theme, but several of the pages we’ve edited will no longer be compatible with the new theme. It would be a big help to be able to open the original in one browser tab while working on the new site in another tab. Separate sub-domains would be ideal.

I searched for the ability to copy the site over to a “test” environment, but this doesn’t appear to be how work is typically done on the NationBuilder platform. I’m interested to know what a typical workflow might be.