Given a driver that includes both capability and command:
command customCmd, [[name: "some setting", type:"ENUM", constraints: ["On", "Off"] ]]
Rule Machine h would expose the customCmd via the Run Custom Action -> Actuator option. However, it does not pick up and honor the constraints. Instead, it allows the user to specify any number of parameters, parameter types (number, string, etc.) and values. This creates a poor user experience because it is unclear what the valid options are from within RM even when the driver specifies the constraints.
Thus the feature request would be for RM to honor the constraints, perhaps even better would be for that part of the RM UI to only offer what is specified in the constraints for that command.
This isn't really possible at the moment. Whilst I understand and hear what you are saying, custom commands are really an advanced feature designed for use by advanced users that have an understanding of the commands and parameters they are intending to execute.
@mike.maxwell - I understand regarding it not being possible currently; however, regarding "advanced users" may be a bit of a stretch in some cases. In particular, not everything always maps cleanly into the defined capabilities. Thus, for some devices, the only option to expose that feature/function is to offer a custom command.
This is particularly the case with more advanced multi-function connected devices. For example, i have fan that has options for focus/diffuse in addition to enable/disable oscillation. The fancontrol capability does not offer any standard commands for dealing with that and the thermostat capability only offers a single command of "circulate" that could loosely map. Yet, these are the types of things that normal (not only advanced) users may want to turn on/off. I also don't think it makes sense to go crazy and overly complicate the capabilities with tons of optional commands as that could create a mess and still not achieve the intended goals.
Anyway, I only ask that you consider adding such a feature and I think it would be helpful for me and other Hubitat owners. Thanks!