Hello- You can, use the From Osnap:and the Tab direction lock
Place the first point,
With the appropriate osnap, snap to the second point but do not click the mouse- when you see the Osnap, just hit the Tab key (tap, don’t hold) This invokes the tab direction lock to that second point.
Type the special Osnap ‘From’ and .
Snap to the second point and click.
5… Type 20 and Your cursor should be on the ‘far’ side of the second point to make the line 20 units longer; on the ‘near’ side to make it 20 units shorter.