Yes, I have found that example and I am trying to adapt it to my wishes which is taxing my Lua programming somewhat, but I will get there. It is using this example where I have found that the LEDs on the buttons will not remain illuminated so some of the shortcuts I have are:
midi:G#-1=lib/masks; show
midi:A-1=iop/colorequal; show
midi:A#-1=iop/toneequal; show
midi:B-1=iop/colorbalancergb; show
midi:C0=iop/channelmixerrgb; show
I changed from ‘focus’ to ‘show’ so that I can see the iop open up/expand.
I had a look at the darktable code (I am not a C programmer) and it certainly looks like there is code there that is designed to set all the LED lights to the correct (on or off) state each time there is a midi event. Anyway I will persevere with getting the X-Touch to work how I want it to. As @martin.scharnke wrote what has been achieved by the developers with this interface is impressive.