How UnDo Boolean Union Long After Lots of Edits?

Greetings! Probably a Newbie question but I did a Boolean Union to create a new image (worked great!) and then I performed lots of more edits/changes on other parts of my project. Now I want to go back and undo the Boolean Union temporarily so I could re-use a part of the original image. Then I will re-do the Boolean Union. I think I have way to too many edits to use the UnDo feature in that I may inadvertently mess up something else. Is there a way to UnDo the Boolean Union (and the other Boolean/Weld functions) in this situation besides the UnDo feature? (which works great if you haven’t done many project changes!).
Thanks!
Gary