You could install a second copy of Gramps with a different application name so that you can have both open at once. The key is to change the second copy so that it keeps its data in a different place. See this post. (That’s Mac-specific but I imagine you could do the same on Windows.) I think I had also posted once with more detail about copying and changing the app but I can’t find it just now. Media files are also a consideration.
Use a different theme in each one so you can more easily tell which version you’re looking at!