[DerekAsirvadem]

Why on Earth would you want to do that ?

OG handles lines perfectly. You need to learn to use he tool. You're used to using a hatchet ,now you've got a small, precise chainsaw, but you still want to use it like a hatchet.

1 Change the length of any line:
- by clicking on any end-point (that the same as a mid-point) and dragging it
- select the line and change its dimensions and position in the Properties:Geometry Inspector
2 Change the various aspects of the line (includes double-stroke) using the Style:Lines and Shapes inspector. Learn every property, and its effect, in this inspector.
3 You can really hot on the dance floor if you learn to use Magnets. First understand them on shapes (rectangle, etc), change the number, make your custom Magnets. Then work with Lines, connecting lines to shapes. Then learn that for Lines, every mid-point and end-point is a magnet. My last example show what happens when I pick up the horizontal single line an d move it (the double-stroke is attached it it, at the middle, a mid-point).
4 Depending on your need, you can setup the grid, and have all you end-points and mid-points aligned to it.
5 Drawing what you want with elegance is simple in OG (seconds, no "fiddling" time when you want to make changes). But if you use it like a hatchet, you'll get a broken matchstick diagram. If you really want to draw line fragments, and join them up correctly, which is no problem at all, just slow, you can do that (minutes). But you still need a decent run through the above. Otherwise about 10 min per complex line to draw, plus unpredictable fiddling time every time you want to change it.