That was extremely helpful advice and I was able to use one of the spare inputs on the UHD722. There's no soft key on the G68J for it, but I can use the Meridian remote to select the new input.

I'll arrange for Control4 to be updated soon. In the meantime, is there any way I can add the soft key on the G68J corresponding to the new input on the UHD722?

Many thanks,
David

Meridian - G68J, UHD722, Rear Speakers: DSP5000s, Centre Speaker: DSP5000C
Naim - NDS, NAC52, NAP300, Front Speakers: SL2s
Other - Rega Planar 8, Lindemann Limetree Bridge II, HDfury 8K VRROOM, Panasonic DP-UB9000, Apple TV 4K, PS5 Pro, Xbox Series X, Nintendo Switch 2