CUIA: Callable UI Actions - "LAYER_UP","LAYER_DOWN"

I was hoping to find something like “SELECT_UP/DOWN” as “LAYER_UP/DOWN”,“BACK_UP/DOWN”,“LEARN_UP/DOWN”

This is for my backup Zynth which is an audio-injector, an external HDMI screen and a wireless keyboard.

I am envisioning an external USB controller based upon an Arduino Nano with encoders, and acting as a USB keyboard connected to the RPi.

I have added this to the stepseq branch. It may require further work on various other parts of the application. @jofemodo will need to review my proposal and decide if we should proceed and what other modules need updating.

Sounds great! Thanks @riban!