How to filter tickets where the customer has responded for more than 'x' days?

If you are a Supervisor who is looking to keep track of tickets where the agent has not responded back to the tickets after the customer has responded, you could make use of a Supervisor rule to add a tag to these tickets. Please navigate to Admin-->Helpdesk Productivity-->Supervisor-->New rule to set this up. 

Say, for Example, the customer has responded for more than 2 days [48 hours] and the agent didn't reply back 

Condition: 

Hours since customer responded greater than 48 

Status is Open 

Status is Pending 

Action: Add tag 

Later, you could filter the tickets in the Ticket ListView by filtering by the Tag.