So you have component Alpha.
And you have component Beta, which as an immediate child of Alpha.
You have assembly Omega in which Alpha is used throughout multiple times.
Is there a method so that if you set the reference set of Beta when Alpha is your displayed part, that it will also change the reference set of occurence of Beta so that when you go out to the assembly of Omega that you will see every occurence of Beta under Alpha set to that same reference set?
I apologize if that is a little confusing.
I can clarify if need be.
Is there a function that allows you to do this in interactive NX? If the answer is no, then there is probably no API function that will do it all for you either. However, through the API, you can change the component's reference set; you would need to find all of the desired components and change each ref set in code.