Porteus

Mostly all german windows users (some linux users too) are used to press 'CRTL+ALT+Q' for the '@' sign.
Any suggestions how to get this running (beside the ALTGR+Q) in Porteus Kiosk?
Is there a possibility to add a custom keyboard shortcut, modify the existing bindings or add a enhanced keymap file?

current config:
primary_keyboard_layout=de

Thanks