This is a method to be implemented for moving a selection based on the displacement between two reference points.

When points are selected, and shift is not held, start dragging from one point to another.  A line will appear, colored differently than the connection line to indicate you are measuring a point displacement.  When the mouse is released on an end point, the selected points are moved according to the displacement between the line endpoints.

Note the endpoint could also be made to snap to any point along a line, though we made decide against this option because it complicates things too much.