One issue with the Keyboard library is that it only works for 7-bit ASCII characters and only for the US keyboard layout. To work around the issue I wrote a library to add international keyboard layouts and Unicode character support.
I scraped the Microsoft website to get key mappings for every keyboard layout. The library includes a header (.h) file for each key mapping and you can include multiple mappings to select at run time. (No, I don't know of any way for the Arduino to detect the mapping currently active on the target Windows machine.)