Is there a way to change audio inputs w/ XR11 or XR15 remote?

Set up my house's Contour today. Enjoying it thus far, however there seem to be some rather glaring problems/oversights/sheer incompetence by whomever designed the remotes.

In both the living room and one of the bedrooms, there are audio receivers. The living room one is truly ancient (mid/late 1990s) and none of the codes work for it. However, I've got an old Logitech Harmony (Harmony 520) running on that setup, so that's not the issue, the one in the bedroom is. Now the bedroom one is pretty old itself (12 years old), and this is the one I'm having issues with getting setup.

I was able to get the remote to work to turn on/off the TV and to control the volume via the receiver. All going well thus far until I need to switch from the Contour box to my PS4 (for my media server and games I play), then I run into aforementioned glaring problems/oversights/incompetence. Doing my share of Google-fu, reading the instruction manual from both Cox & Xfinity and perusing both forums, I can't seem to find a way to get the XR11 or XR15 to be able to change inputs on the receiver (HDMI out from all devices runs to the receiver, then HDMI out of the receiver runs up to the TV). I figured SURELY I'd be able to switch the TV input button to toggle the A/V receiver inputs instead like with the ancient remotes that came with the Scientific Atlanta/CISCO boxes; but for the life of me I can't get it to do so.

For the moment, I've got my XR15 to run the audio up/down & cable channels as well as powering on/off the devices, but I've got to have my old grey Cox remote simply to toggle back and forth between inputs on the receiver (cable box & my PS4). If the XR11 & XR15 CANNOT do this, is there a remote that Cox can ship me that WILL do this? Or are my only options being forced into having to purchase another Harmony (or a Harmony hub) or having to keep my old grey cox remote around JUST to change the inputs on the audio receiver? Now to me it doesn't seem like too much of a leap of logic to think that plenty of people would run some sort of home theater setup in their home. Or if not a home theater setup, at least running a receiver to run surround sound in one or possibly more rooms of a home, and likely more than one device on a TV. Especially a setup that runs HDMI through the A/V receiver as that seems to be the standard for the last... Oh I don't know 10+ years or so. Sorry if I seem to come off as angry, I just can't imagine what the engineers on this remote were (not) thinking when they designed the damned thing. Any help is appreciated.

Thanks,

Grant