If you set a category image/logo the category description (first paragraph of About topic) shows up in large text next to the logo. That might be sufficient for what you are looking for? Have you seen that feature? It’s found under Edit > Images on the category page.
I was looking for the same thing, Pinned Category Banner - but the logo image will work as well. Of course you end up with an image/logo that you have to come up with / live with…