I don’t think this one’s been requested before, but if it has then please consider this my +1:
If I move a stave/system as far as the top of the bottom padding, the read-out says “0mm”. If I keep shunting further south, there’s no indication that I’ve gone lower than 0; the read-out continues to state “0mm”. Could this be rejigged in such a way that the distance from below the top of the padding is accurately stated, e.g. “-1.5mm”, please?