Add an index-corner on a pad?

Hi, I’m creating my own footprint for the MC33926 motor driver. (http://www.farnell.com/datasheets/1844099.pdf)

It is a PQFN 32 pins chip, with a big pad in the center for ground. The center pad is mostly a big square, but one of the corners has a diagonal cut to indicate pin 1.

How can I add a pin in the Footprint Editor that has such a diagonal cut in one of the corners?

You will probably have to use multiple overlapping pads anyway to get the solder-mask right [mesh of squares], so you could try using a trapezoidal pad to mimic this - if it is worth the trouble.

Using a square-shaped notch would probably be easier, or make the corner pads a bit longer.