Thanks for your comments.
No. I do not wish to move the arrowhead up or down the line.
Yes. I do know how to move the line, but that is not what is wanted in this case here. I'm wanting to extend or retract the line and rotate the line (with the pivot point at the opposite end of the line) freely by dragging one end of the line with the mouse cursor.
Yes. It appears you have misinterpreted my original post.
lepr has posted the correct solution! Thank you!