If you want to add an action that you are missing, the best way to do 
it is to add a custom action to the existing Behaviour (=> please see 
RB Help > "How do I .." for step by step instructions).

I don't own a Harmony One, so I can't say anything about it. But if 
it's anything like the other Harmony remotes, you should be able to 
set up your remote to send IR codes of different Apple Remotes (each 
having its own, different remote ID). When using Apple's built-in IR 
receiver, Remote Buddy can distinguish Apple Remote IDs. Remote Buddy 
also supports mapping different actions to Apple Remote buttons 
depending on which Apple Remote ID was sent along with the button 
code. With a learnable remote, you can use this to your advantage to 
effectively have more than six buttons available for mapping.

You can read more on this in an article written by a user: 
[removed 2011/01/18]

Best regards, 
Felix Schwarz