Apply Stretch commands to all measures involved in any selection
S5 - Suggestion
Discussion at Event doesn't reach its logical recipient
Related post regarding Insert One Measure
Personally, I'd rather see the ability to apply stretch to partial measures. I could imagine a future revision of the layout algorithm attaching stretch factors to segments as opposed to just measures. This could potentially be a significant improvement over the current method of adjusting leading space or positions of individual notes/rests. But perhaps an even better short-term suggestion would be, allow the stretch command to actually work as a leading space adjustment! That seems far more useful and also far more intuitive.
On the other hand, better still would be improvements to the spacing to render any of these sorts of adjustments unnecessary.