How to add scheduling rule after service is running?

I’ve got a service running, and now I need to add a scheduling rule (eg. exclude certain labels, so it will avoid certain hosts).

Where in the UI can I add scheduling rules?

I can’t find it in the webui for a service that is already running. Though, for a NEW service I use the “Scheduling” tab all the time.

Ditto for adding custom labels: How do I add new labels to a service already in production?

“Edit” option for a service provides only Name and Description.

I’ve always just cloned the existing service when I need to make a change like that.

Yes, that’s what I’ve done in the past.
However, now I have a storage/glusterfs service with live data stored in it. And so, I don’t want to take the service down just to add 1 scheduling rule, which is really just metadata for the service.
Also, I’m thinking a data migration of volumes would be needed, which is even more disruption and work.

Can I add a scheduling rule using the API? (instead of the web ui)