Select the Window with the line annotation that you want to move.
Under the Drawing pull-down, select Line Annotations, Move. All line annotations in the Window are now selected, as indicated by the handles on the end of each line segment. Also, notice that the cursor is now a four-headed arrow.
Click and drag the line you want to move. Let go of the left mouse button to set the line in place. You can repeat this process indefinitely until you press [Esc] to exit from Move Line Annotation mode.