Do you want the customer to see the history of the ticket? Ideally secret link ...
The response of the support staff member only contains the last response, which does not suit if the ticket and its solution are longer in more steps / responses ...
Only {customer_request} can be inserted in the email notification configuration but you can not paste the entire history as it is sent to the CC if it is used.
Can both customer and CC be at the same time? This would be a temporary solution.
Thank you.