You can create subjects only visible to tickets. Or alternatively, you can use the same subjects that you use for Knowledge Base articles or Community Portal threads. If you use the same subjects, there will be a connection between the tickets, articles and threads.
First of all, to add a subject, please click on the "ADD NEW SUBJECT" link from the admin menu under "SUPPORT -> Subjects".
After clicking on this link, you will see the interface below:
If you want the new subject to be visible only in tickets, select only "Tickets" in the "CONNECTION" field:
After you fill in the other fields, click on "Add Subject".
If you have a specific agent in your team, who is responsible or qualified in this subject, you can add this agent in the "ASSIGN TO" field.
This way, when a ticket is opened with this subject selected, the selected agent will be assigned to this ticket automatically and the agent will be notified. If you add multiple agents, the system will assign the ticket to a randomly selected agent.