It would be incredibly useful to be able to assign a button that sets a “Zone Source Selector” to a specific source. If that source is unavailable, the button could automatically gray out, and when the source is active, the button would illuminate.
Ideally, this could be tied to the label within the selector rather than a fixed “Source/Preset” number. That way, if the available sources change or are reordered, the button would still point to the correct source instead of triggering the wrong selection.