ok problem solved at least for me.
i just installed "modify your on-screen keyboard layouts 0.0.2-2" and now i have a ß if i hit the blue arrow and Ctrl.
anyway still strange that this letter isn't there in the original layout. still a lot of space if you use the shift key.
it isn't a problem if you use the virtual keyboard, right. but did you tried the real keyboard?
or even with the (blue arrow)+Ctrl ?