Please bear with me, I know this is a lot of text, but I would like some input.
So I played Minecraft Java Edition a lot when i was on parental leave 5-6 years ago (baby slept a lot and daddy had to do something with his time...) and now I suddenly had the urge to pick it up again. I used to put lots of time and energy into my little palace which i built in survival. All those trips to the Nether, crawling around mining all the nether quartz needed for my main entrance hall... I also built a gargantuan mob farm tower and an iron golem farm. These structures where built all legit and I'm quite fond of them, because of their uses.
The thing is that I would now like to move those three structures into a new world, with all the wonders of the latest updates. The world where they stand today is explored for hundreds of chunks in every direction. Back in the day I used MCEdit to move my builds to fresh, new worlds when updates required it, but I can't seem to get it to work now. I understand that there aren't really any map editors being updated anymore (why though?), so I thought I'd use an editor with outdated version support and do the work in older Minecraft JE editions.
My idea is to start a world with a carefully chosen seed, in an older update/edition (like 1.8 or whatever would work) via the launcher and then explore only as much as I need to fit in the structures - thereby ignoring that these chunks generate with old parameters. Then I'd use a map editor to import my structures into this world. Lastly I'd open the world in the newest version of Minecraft JE again and enjoy my pretty palace and explore the map to "uncover" chunks with new material...
So far so good, but I can't get this to work as I want it to. For starters, MCEdit doesn't look much like I remember how it looked. For example, I remember how I selected a bunch of blocks and could then move the selection along one of the three axises, represented by red/green/blue arrows. I could also place big yellow pins/tacks on the map for spawn position and other points of interest. None of this is possible in MCEdit, regardless of if I use MCEdit2 (or whatever it's called nowadays) or MCEdit Unified. What did I miss? Am I going about this the wrong way? Help...?