Do you have your Harmony hub in ST? If not, try setting this up. It’s been a while, but I think you can then use it to control volume…I know you can control activities. If it can’t, I’m not sure if Anthem or Denon have ST Edge drivers.
I don’t have the driver installed on my hub at the moment, but the first post of that thread talks about how you can discover the commands and make “buttons” that can be used for automations/routines.