On the Mac there is an helper tool that let you see the keyboard key mapping, when you press modifiers, so it's just a matter of looking at the German keyboard layout and what it corresponds to in the American keyboard layout
For example { from a German keyboard would be obtained by pressing alt7 on an American keyboard so you could possibly mimic this by sending those two key press and in the receiving OS as the keyboard is configured as German, it would be seen as { ?