RE: Tuning: Adjusting Nock Position
The reason one does not move the rest is that the bolt elevation is intended to let the arrow contact the string at about the center of the free bowstring, or the fastest moving part of the bow string as the bow is shot (as said before, “speed sells”).
If the serving is not braded the loop should screw up & down, like a nut on a bolt, but it needs to be tied very tight with tools to stop movement when the bow is shot. If it moves sometimes, just pull it back in place, the elevation will not change.
Sometimes one may need to tie the upper knot in one direction and the lower knot in the other direction for balance. The knots can be half hitch or clove.
When starting out, one will want to use the center-shot & nock elevation suggested by the maker or seller. And you should not stray far from what they suggest before you look for other glitches.
In other-words before you move something over 1/8”; ask-someone in the know, again about what you got going on here.