Mode buttons appear to all be there with the exception of "Mode Surround".  Have this button on my Harmony remotes, and want to map buttons to switch back and forth between the surround decoder and stereo for the Apple TV.  Any way to get this added without going through the entire remote learning process and creating a whole new device?

I believe you can set up a new device with just the missing buttons you require and then use it in your assignments and macros alongside the original. There are way too many buttons on the Marantz remote to set them all.