Sometimes you can use only one hand to access the KeyStep pro (e.g. you are playing another instrument, you are disabled, …)
It would be nice if the SHIFT button could be virtually held down, e.g. by a quick double-press.
The light under the button would be on to indicate that it is (virtually) pressed, and the whole UI would shift just like it has been physically pressed.
The release would happen with a single press of the SHIFT button, or by using any feature for which it makes sense to use shift with it (e.g. change the arpeggio timing, the scale, nudge the notes, etc…)