Id take this one step further and like to be able to add a text-based line in between lines so I could create a bold header and have sections like this -

Widgets

1. Sprocket Alpha     This is the sprocket for Alpha Gears     x 1    100.00     100.00
2. Sprocket Beta        This is the sprocket for Beta Gears       x 2    100.00     200.00

WingDings

1. Winding Alpha      Winding for Alpha Gears                       x20   100.00    2000.00

This would allow invoices to be so much better organized and visually appealing.