GGU-CAD: "Extend" menu item
After going to this menu item or pressing [F7] the length of a line can be edited. Click the end of the line to be edited. A new length for the line can then be entered, the angle of the line is retained. If only minor changes need to be made it may be necessary to change the snap radius in "Preferences/General", otherwise it will always snap to the old end point.