Multi-endpoint dimmer unsupported?

Here are some tips to help you get started

and you can refer to the ST Composite Device Handler docs for an overview...but be aware, the API is not exactly the same on Hubitat so refer to the above information from @chuck.schwer on how to use the Composite Driver API calls.

https://docs.smartthings.com/en/latest/composite-devices/

Good luck and let us know if you have any questions. Lots of helpful folks here in the community!