User Access tab has settings to control the access for different User roles.
The option with the label : Who can access Help Desk? is the basic way to control the User Access to your Helpdesk. You can select who can access the Helpdesk : logged in users or anyone.
Under the Who can access Help Desk? option, you’ll find listed, all the editable user roles with categories listed near them.
An example of hiding SHORTCODES category to users with Subscribers user role.
You can select All or specific categories that the user should be allowed to see. The default option is All for all User Roles. The category list and the search results filter only the selected categories, giving you the control you need.
You can use Product names and categories to allow Product specific documentation and setup User Roles Editor or similar plugins to create User Roles for different users.