To me it seems quite random what value you chose to toggle the modifiers. Sometimes its 1 (M7 for shift and M4 for deck C mode), sometimes its 2 (M8 for deck D mode) and sometimes its 3 (M2 for fader juggle mode). Is there an idea behind this that I am not seeing?

I think its important to try and be consistent here as if this is done cleanly its easier to do stuff like bitwise operations to fold multiple toggles into a single modifier as I explained here.