Update:
- The pregen command's default radius now adapts to the world's border instead of being hardcoded to 29999984, ensuring compatibility with custom world borders.
- you can use this if set your world border manually using /worldborder set #
- Usage: /pregen <ParallelTasksMultiplier> <PrintUpdateDelayin(Seconds/Minutes/Hours)> <world> <Radiusin(Blocks/Chunks/Regions) or default>

Command Examples:
/pregen 6 5s world 1000b
/pregen 2 2m world_nether 500c
/pregen 1 12h world_the_end 100r
/pregen 4 10s world default