You can hide a category from the table of contents and other navigation by editing a category and choosing Hide from navigation under Content Restrictions.
Articles inside a hidden category are still available in search. To also hide articles inside the category, you can create a reader group called something like Hidden and restrict the category to this reader group. You could alternatively mark the articles inside as Hide from navigation but you need to do it one by one.
To restrict a category or sub-category to certain readers, create a reader group and restrict the category to the reader group. When a category or sub-category is restrict to a reader group, only readers who are part of the group will be able to access the category.
Reader groups restricts waterfall, meaning that if you apply a reader group to a category, the same permissions will also apply to any content inside the category. If you want to restrict everything inside a category, you only need to set the reader group restrictions on the category as the restriction will automatically be applied to the content inside the category.
When you delete category, it will also delete all the content inside the category. If you want to delete a category but not the content inside it, move the content inside before deleting.
If you delete a category by accident or need to bring back a deleted category, you can use the API to switch the status back to active or contact support so we can do it for you.
Custom content categories are the only categories that show up in search since they are treated like an article. If you are using default, blog, or topic-based categories, they will not show up in search results.