Java structure NBT guide
A .nbt export saves your build as a normal Minecraft structure that you load with a structure block.
Minecraft saves its own villages and igloos this way. Put the file in your world folder, place a structure block, type the name, and the build appears. No mods needed.
Before you start
Minecraft Java, creative with cheats on
Access to your world's save folder
A structure block, from /give @s structure_block
Steps
Export the structure
Pick “nbt single” for one file, or the chunked option to get 48 x 48 x 48 pieces of a big build.
Add it to your world
Put the file in your world's structures folder. If the world was open, close it and open it again.
Load it with a structure block
Get a structure block with /give @s structure_block, set it to Load, type the structure name, then load the build.
Export it by choosing nbt single in the converter’s export menu.
Open converter