I assume we are talking about the surface editor here. There isn’t much more you could do.
If button X sends out to cubase MIDI message A, and the same button with shift pressed sends another message B, you could also create double the elements in your remote and have them both on it. (Button X, Shift Button X)
Will definitely look cluttered, but it’s another one page workaround.
I’m sure there’s a much better solution via scripting, but I can’t help with that, you’ll have to wait for the right people to answer.
Also, have you seen this? Maybe it works? Apart from the added octaves, the layout seems the same?