There is an nvidia-settings binary, normally installed by default when you enable the nvidia module, and it has a disable option that uses camel case: hardware.nvidia.nvidiaSettings.
Given this:
Make sure to allow Unfree Software. The unfree NVIDIA packages include nvidia-x11, nvidia-settings, and nvidia-persistenced.
Maybe @koppor is using an allowUnfreePredicate snippet that gets names from a list of packages, and gave it nvidia-settings, assuming that would exist?
Detective work isn’t what I’m here for though, please share your code if it’s not working!