This post (and Brad’s LinkedIn post that goes into the details) should help. client settings automation?
Another technique I’ve used is to attach the key:value pairing as a text file that is attached to a Custom Site; then you can have an Action that reads the file to retrieve the mappings, search for the line that contains its relay, and assign the value as a client setting. Workflow considerations for using REST API to set Client Settings on a system-wide scale
Edit: added Brad’s link