Is there a way to register more fingerprints for TouchID on a MacBook?
One option it to alternate fingers back and forth while registering them. 
ie. place your right index one press, then right middle one press, then right index again for one press, etc... Do that the same when you get to the edges. You'll be able to unlock using either finger stored in a single memory location.

I currently use this, it does work, I've heard of people registering several finger prints to a single location on iOS. I'd rather register them discretely though, hence why I asked this question.

I suspect it's accuracy goes down as the number of finger prints goes up, but I haven't seen that with just two prints on one memory slot.