Yeah, support kinda sucks. I can advise you to just explain the problem again. Hopefully, they will read the reply more carefully this time.
I actually tried playing around with the registry keys, however, to no avail. Moreover, there are maybe 10 places, where the keyboard layout is specified and God only knows which key does the iCUE app needs. It may be possible that it doesn't detect the layout through the registry in the first place.
I also looked into decompiling the plugin dll file, however, it appears to be written in either C, or C++. Even if I guessed the correct compiler that was used to compile the dll, decompiling C/C++ code is a huge pain in the butt. I even tried looking into the CUE SDK. I spent about 2 hours with it and couldn't get it to lit up the problematic keys. I could spent another several hours looking at the assembly code that's executed, when the program is ran, however, I really have better things to do with my time.
Bottom line is, this is Corsair's software and Corsair's bug, so they should be the ones spending time fixing it.