Exclude child categories only?

Hi Guido — This really is a beautifully simple plugin and it does just what I was hoping for. But it would be even better if there was a way to exclude child categories — or better said, to have them show up under the parent category. I’m not so great with code, but if you could give me an idea, I’ll give it a try.

https://wordpress.org/plugins/very-simple-knowledge-base/