Currently there is no way in MaxScale to refresh ssl certificates with new ones. In MariaDB, whenever a new ssl certificate is refreshed, we can just issue a flush ssl command, and this will take care of it.
In order for MaxScale to be updated with the new certs, a service restart of maxscale is required.
I did some investigation and found this capability was added to MariaDB at the end of 2018. Could this same concept be implemented in MaxScale?
Here's the MariaDB feature request for this same issue, which has already been addressed and it works.