Hmm actually looking at the list even the windows shortcut for creating calculated fields isn't even on there. As Alt seems to be a windows only function, it seems to be replaced by 'option' a lot of the time on Mac.
Could you try maybe Option A C? Unfortunately I am not currently using a MAC to test this out!
No that doesn't work It seems like on the windows side each tab has a hot button but that doesn't appear on the Mac side. Anyone else?