Talinb:
When using Arduino IDE, by default it configures it to type in English, but I need it to be German.
For minor layout differences, edit the 'asciimap' table in Keyboard.cpp.
WARNING: For any characters that require the AltGr key you will need to add code to press that key. I think it is KEY_RIGHT_GUI or KEY_RIGHT_ALT. It looks like the highest key code used is the /? key (0x38). As long as the key codes are all under 64 (0x40) you could use 0x40 for the AltGr flag (0x80 is the SHIFT flag). Use the SHIFT code as a model.