Amulet editor is in development right now and seems pretty promising, it's lead by some of the original developers of MCEdit. I think the best option right now is Worldedit (it has a fabric version) plus Euclid so you can see what you are doing https://mobdro.bio/ .

ive always wondered about a more simple way to do this. let me know if someone finds something haha, i've always used schematic blocks & moved the nbt files from one world to another, but you're only allowed a small selection so i end up making puzzle pieces almost, then with world edit stitch it all together and paste it ;p

Mcedit?
Amulet editor?
Use Worldedit and make a schematic

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