@danan72: have not checked this, then I have no solution, but assume, Amazon has simply hidden this file somewhere else in 3.4, just to getting us annoyed.
- concerning effort for the shop, a clear no from my side, I have no use for it, would just be for having a real completely localized K3
- physkeyb: I only have modified keyboard.txt, no changes in keyboard-european.txt, but for me the double click works fine with my "Umlaute" as I configured, so no switch necessary. Before there was only the config.txt, only one file as well. I used phsykeyb before as well and its one of the most useful hacks for typing in german.