Adding New Categories

Because there are no posts in them.
Most themes by default do NOT show empty categories.

Got it.

Thanks.

What happens if a new user wants to make a post to a category that’s already set-up but not visible?

…eg my website https://www.footballmuppets.com/

To clarify: Category’s without posts tend to not be shown on the blog’s sidebar or category list. However, those category’s WILL show up in the Post Editor page so that they can be chosen.