I like to turn the volume down on my a/v receiver before turning it off. However, the off button on the Harmony One just turns it straight off. Does anyone know if it is possible to change the functionality of this button to add an extra command?

Obviously, I could create a new activity for powering off but would prefer not to. Also, if I did that I'm not sure how to set it only to turn off the devices which are active - if I tell it to turn everything off it will end up turning on the devices I haven't been using.

All thoughts appreciated...

In any Activity that uses the receiver, include the commands you need as Additional When Activity Ends.
Activity> Settings> Review Settings> Yes but....> Save> Next> Next takes you to the location for that.

That would work but it would also turn down the volume when switching between activities which probably isn't necessary.

The best solution would be to have a separate activity that only includes the A/V receiver and put the volume down commands at the beginning or end of the activity. When you select that activity it will turn off any devices that are on except the A/V receiver and since you're using the harmony's Smart State activity switching it will know not to send power toggle commands to devices that are already off.

To use it, select the activity Rcvr Vol Down first, then hit the OFF button.

If your device (AVR) supports the discrete PowerOn and PowerOff commands and is configured accordingly, then another possibility is to add the extra commands in the device Power Off configuration (by selecting the option "My device needs more than one command to turn it on and off"). However, the limit is only 6 commands (allowing for 5 extra commands preceding the final PowerOff command).