Alright, I finally found I could use a custom action in RM to set colorTemp independently on a dimmer. Would be good if “bulb” would be added to the list of capabilities under custom actions, in RM, just to narrow the devices to bulbs alone.
Forgive me if I missed the point here. It sometimes takes me a while to get my head around this stuff. Was this change supposed to allow take the rule's setLevel as a null value? I guess I don't understand how transition time is a factor.
The rule (Basic or RM) for setting "Dimmers and Bulbs" is passing parameters to Bulb Temperature/Bulb Color and Bulb Level, and I don't see where transition is affected (but again, I probably don't understand well enough).
The RM rule for Custom Action does not have a device capability for Bulb, so Dimmer or Switch must be used, and then a single parameter can be set. I was simply saying that having the custom capability of "Bulb" would narrow device selection. A task for the RM dev.
What I think would be helpful is if your driver could use the Basic Rule of device type Color Temp Bulb/Color Bulb and not pass a value if the Bulb Level field is null. That would keep from having to build the more extensive RM custom rule.