Can I edit a closed ticket to add information?
No, tickets in a closed status cannot be edited. Only tickets in solved status can be edited before they get closed via trigger or automation.
Only follow-ups can be created from closed tickets. Ticket properties on closed tickets cannot be changed, furthermore business rules such as triggers and automations do not act on closed tickets at all.
For more information, see About the inborn system ticket rules. For more questions about Closed tickets, see the articles below.