Question:
Is it possible for users not to be able to choose the category and/or priority of their ticket?
Answer:
Yes, you can make certain categories available to technicians only or to specific users only. Regular users will not be able to select those categories.
1. Sign in as an administrator and open the Administration > Ticket categories page.
2. Click on the category to be modified.
3. Select "For technicians only" or "Specific users" in the permissions settings. Provide the list of users with access in the "Users" column if you selected "Specific users".
Now save the changes, and you are done.