Found those topics but none of them was for a specific category…
https://meta.discourse.org/t/how-to-add-external-link-on-top-menu/9508/6
https://meta.discourse.org/t/best-way-to-customize-top-menu/35336
https://meta.discourse.org/t/after-add-a-link-to-top-menu-how-can-custom-the-link-showed-on-mobile/20679