While the plugin did use to include pregen before it felt out of place for me and started crowding my codebase. I decided to move it to a stand alone plugin to simplify the plugin and make it easier for me to manage the different features. So you can pregen with that instead
https://www.spigotmc.org/resources/chunker.117744/
The pregen since moved to Chunker has been improved a lot since it was first intergraded into SkyGridx so feel free to give it a try and let me know if you run into any issues :)