Currently, if a Learner has completed a Course and achieved a Certificate but is then re-enrolled into the same Course, the previously achieved Certificate is not visible in Manager Experience even if the original Certificate is still valid. Seeing expired Certificates would also be helpful.
It's important for a Manager to see all the Certificates his/her team members have earned - be it for re-enrolled courses or expired certificates. Expired certificates can trigger an action from the Manager to ask the team member to re-Certify themselves.