Forgot to put down that I'm running 2.4.2

Yeah no that can't be done. Each blog has to have it's own category list, and each category in the entire installation needs to have it's own "cat name URL" (or something like that). So you would have to duplicate your category names for each blog ... and make sure each one has a unique cat name URL. So like you can have 82 blogs with a category called "sports" but only one of them can have a cat name URL of "sports".