And on the second aspect of that, of drawing arbitrary lines: you can effectively do that by creating two shapes and connecting them. You would then make the shapes as small as they go (it will end up as a circle) and remove any settings that make them visible. They now act as anchor points by which the ends of the line can be moved, and by dragging on the line, the whole thing can be moved as a unit.
Here is an example Scapple board. I used this for a while as a way of keeping track of the things I needed to get done in a day, as well as documenting how I got them done. It has a couple of lines on it, one stylised as a large arrow, the other a dashed line. The idea of having a sideboard area like that for templates is something that could help out here, as you could have a couple of different line styles and orientations set up and ready to duplicate.
daily_todo.scap (20.4 KB)