You may also find the Curve tool useful (Drawing toolbar: AutoShapes | Lines
| Curve). It's not immediately obvious how to use this, but what you do is
click to start the line, and then click again for each bézier point;
double-click to end the line.
The tool creates a vector shape, and once you've got it roughly defined, you
can right-click and choose Edit Points and drag them around to fine-tune the
shape. You can also add and remove points as needed. It took me a
regrettably long time to discover this tool.