By default, all
Customization > Service Desk > Tickets >Classification > Categories.
Select one or more categories to hide, right-click the selected area, and choose Mark as Internal from the pop-up menu.
NOTE: Hiding a parent category does not automatically hide its children. You should select each subcategory individually to hide them as well.
TIP: You can “publish” internal categories by selecting Mark as Public from the pop-up menu.