Hello,
Organizing mods is a nightmare and I've always wished I could use subfolders named with categories to place different types of mods into in my /mods directory but Forge doesn't like when I try it.
This would be easy to implement with dir.listFiles()
https://www.baeldung.com/java-list-directory-files
https://www.technicalkeeda.com/java-tutorials/java-file-listfiles-method-example
Example
/mods/
folder-named-worldgen/mods-about-worldgen
folder-named-mobs/mods-about-mobs
folder-named-biomes/mods-about-biomes
etc.