Those docs are still not complete.
Here are two more hints I found out by poking around:
To tap the button that has "," and "!" you need to use ",!" value for keyboard_enter_char.
Unexpected, right? Not "," or "!", but both of them in this particular order.
Same goes for ".?"
But I still have 1 button I have no idea how to tap using scripts.
It's the "more, symbols" button with "#+=" title, the one you see when going from letters pane to numbers pane.
Anyone knows what's the reference value for that button?