Can I bind multiple key shortcuts to the same action?
Solution 1:
It seems like adding a shortcut in the Keyboard preferences will override the built-in defaults. You can use Keyboard Maestro (a paid app) to add such things - easiest would be to add a trigger for the alternative combo which translates into a menu action or into the original keyboard shortcut being sent to the application of choice.
Solution 2:
I ended using Karabiner probably not as powerful as Maestro, but for simple needs it does the job beautifully.