The console doesn't open in Crusader Kings II, if I'm using a Mac. I have tried everything and I have never seen it open.
As discussed in your other thread, it is certainly possible to open the console on Macs in general - there seems to be something peculiar about your particular setup though. Which keyboard layout and OS X language do you use?
The grave character ` works on my US keyboard/Aus English OS X language. You have the Section symbol § - which by itself should work too. But to generate that character Option-6 ought to work; I just tested both that and ` right now and both worked fine.