Pretty sure this got overlooked! Don't be afraid to bump the issue with the results on the latest stable version!
I'm no C++ coder, but as far as i understand plugin documentation is still unsupported. For example, Godot Jolt doesn't have it either because of this.
It is possible that you are facing a half baked feature and you are indeed doing nothing wrong.
@mihe , excuse to bother you, is this still the situation with plugin documentation? i get this question a lot.