GG,
It is not a breathing exercise and I'm afraid it requires brief but strenuous activity. I had reported this method a number of times in the past but I have never heard of any disciples of this method, though I am confident it would work for some of you sufferers.
I called it the Rapid Respiration Elevation method (RRE). No doubt that the specific exercise is not important but the rapid elevation of respiration seems to "burn out" the instigator of that evening's RLS.
Following is how I accomplished it which I discovered accidentally out of desperation one evening. I had been performing for many years aerobically modified exercises for my poor back. I included push-ups just for the cardiovascular benefit. I had managed to achieve one-hundred successive push-ups daily. That many push-ups will rapidly elevate respiration regardless of any previous exercises.
Not being able to get to sleep one night even with the Sinemet I, for whatever reason, performed a hundred push-ups. Following the push-ups for the next three or four minutes my legs went just nuts! It was RLS on steroids. But, once my respiration returned to normal I was able to drop off to sleep like a baby. I never used Sinemet or any other RLS prescribed drug from that time forward. On rare occasions I would have RLS symptoms about twenty minutes later but would successfully perform the RRE a second time. Only once or twice did I have to perform the RRE a third time and never a fourth.
To my knowledge no one has reported using my scientifically

achieved RRE method. Likely others could achieve rapid respiration elevation using other, less physically demanding, exercises. I would be interested to learn if this works for others.