DestinationDirection
It gives you the direction (yaw) towards a given position. You input the destination X and Z coord and it calculates the yaw that you should move towards to reach that destination in a straight line!
Located right in Game Menu
the Left textfield is for the destination X coordinate. the Right textfield is for the destination Z coordinate. The Calculated yaw you should travel in is calculated and displayed below.
Calculations in Code
heres a code snippet. its simple. gets the relative position of the destination, finds the angle associated, and then turns it into a final yaw.
Yaw in F3
just pointing out where Yaw is in F3 (debug) menu. Its in the line that says "Facing". in those parentheses, its the left number. So the yaw in this image is 71.6 degrees. :)
another demonstration image.
Lets say im in the nether and i want to go to nether coords -140200 90400, i just put those numbers in, and it says i should move at yaw 57.2 degrees. So i would exit the menu, rotate until my yaw says 57.2 (or close to it), and then elytra fly forward!