There's an easy new way to add certificate authority (CA) certificates to your SSL/TLS configurations on InterSystems IRIS 2019.1 (and 2018.1.2) on Windows and Mac. You can ask IRIS to use the operating system's certificate store by entering:
%OSCertificateStore
in the field for "File containing Trusted Certificate Authority X.509 certificate(s)". Here's an image of how to do this in the portal: