A temporary world is generated on the fly with the schematics you wish to choose from.
Left clicking on a structure will load it and close the temporary world.
Right click will add it to your current multi-clipboard.
Benchmark after optimization (no conversion):
2000 schematics (total blocks: 5,078,400,000)
run 1: 309ms initialization + 271ms packets
run 2: 72ms initialization + 3ms packets
Limitations:
first use of the command is delayed as it caches the relevant data
slow when trying to visualize more than a few thousand schematics at once
lighting/physics is not present in the temporary world
TODO:
optimizations
interface