Actually less of a shortcut, more of a quiet-cut.
Yesterday I tried out the newish shared use paths linking Robertson Gait (off Robertson Avenue) and Slateford Gait (off Slateford Road). This basically cuts through the new development of flats on this site.
Could be useful when heading Slateford to Gorgie if you can see that the lights ahead are red or about to go red.
Or coming the other way it would remove the need to get into the right hand lane whilst going up hill. Still requires a right hand turn into Slateford Road of course.
Basic paths added to OSM, although could do with adding more detail.