This is another example of how developer hostile AmigaOS has become.
After finding examples of software that does use NSD, I see they all reference devices/newstyle.h which doesn't exist in the 3.9NDK.
Why is it all secret and paid for these days? Assuming I can even buy a developer CD. The RTG lockdown from a 3rd party developer is stupid enough, but a 10+ year old public interface in the OS itself?
I may end up doing TD64 just because I can do it without paying to ship a hard to find CD from Europe or becoming a pirate.
This is why we can't have nice things.
Those two choices aren't mutually exclusive. I bought my dev CD about 10yrs ago from a well known European Amiga dealer and it is quite obviously a CDR with an inkjet printed label stuck to the disc.