Apple - How do I do a diagonal-arrow keyboard shortcut?

I suggest you to open your keyboard visualizer (by clicking on the flag that is near the clock in the menu bar).

This will make appear a window with a keyboard representation.

If you press the fn key, you'll see that the ← will become a ↖︎ (Home key) in this window while → will become ↘︎ (End key).

That's it: just press the fn+← or fn+→ to obtain the diagonal-arrow.

These are the home and end keys on OS X.

• On full keyboards, there are keys designated to home and end.

• On notebooks you can press home by pressing fn+left and end by pressing fn+right.

  Additional key behaviors

  • The Numlock key has been removed on Late 2007 and later Mac notebooks.
  • Home key functionality is performed by pressing Fn (Function) and Left Arrow key.
  • End key functionality is performed by pressing Fn and Right Arrow key.
  • Page Up key functionality is performed by pressing Fn and Up Arrow key.
  • Page Down key functionality is performed by pressing Fn and Down Arrow key.

  ^{Source: http://support.apple.com/kb/ht3164}