This userspace keeps my userdefined codes. I work on a ANSI keyboard on a Danish macOS system. I believe this code might be relevant for similar users. A big shout out to user spacebarracecar for the ideas on how to map keys, which served as the basis of this code.
By daily work involves a lot of coding. I find an ANSI layout superior and decided to buy a QMK keyboard. However, all PC's here in Denmark are set to input language Danish. Even though I could simply set input language language to US international, I find this inconvenient. I instead decided to map my keys so the ANSI keyboard would will function as expected when the OS inputn language is Danish.
Tracking the current state of the shift code is nessesary for it to work. User spacebarracecar has documented the idea thoroughly and should serve you as a starting point if you wish to implement this code. I modified the code to suit Danish input language. Additionally, a couple of functions were added to accomodate the altgr key.