Merging parts of two maps into one

I have two maps that I'd like to combine into one. They are, technically, the same map but one has been updated considerably and has a lot more content in it -- but some things I really loved in the old map were removed. There's also some chunk errors in the updated map because it was converted from Bedrock.

Anyone have any advice on how I can take all the disparate pieces of these two maps and combine them into a map that has everything I really want? My only guess is MCEdit/WorldEdit, but I'm not knowledgeable about any of that yet.