Currently, there's no way to load and initialize scripts during world generation; you have to copy the scripts into the scripts folder manually after the world is generated, then either relog and/or use script load to load them afterwards. This is unlike datapacks, which can be loaded, initialized, and made effective during world generation.

I propose adding a seperate button that takes you to a seperate selection screen whereby you can drag and drop script (.sc) files, then select which script files you want to load as the world is generating, similar to data packs. This could be useful for scripts that modify world generation, but can also apply for some other game mechanic implementations as well, as well as if you are running a no-cheats world.

I did think about it and the more I thought about it, the more I was convinced that apps should not mess up with spawn chunks generation. I know that it would be cool to have that, but that could be dangerous too.

It's not just world generation that can be affected by allowing scripts to be run as the world is generated. You can still have scripts that add / change new game mechanics even without affecting world generation at all. For example, a custom health / hunger system, mob levels for more difficult mobs, per-player bulk item storage (think /dank/null), a full Gregorian calendar system, and more.