Can I create articles under the Help Center categories?
No, it is not possible to create articles directly within categories. Articles can only be placed within a section or subsection if you have Flexible Hierarchies, and sections within categories.
As a workaround, create only one category and restructure your FAQs to have multiple sections inside that single category. Help Center will display the sections on the Home page if there is only one category where all the sections reside in.
For more information, see the article: Getting started with Guide: Setting up.