I'm no modder, so forgive me if this is a dumb thought:

I think when you don't need "pack.meta", you should use "en_US.lang" (resource format 2) and not "en_us.lang" (resource format 3)... currently the Controls menu shows the unlocalized names for your new key/category. Or maybe it's something else entirely =)

Great mod - essential to packs - keep up the great work!

Ah, yeah... I swear it was working in dev.