@Override
	protected boolean isEnabledForContext(NavigatableActionContext context) {

		Program program = context.getProgram();
		ProgramLocation location = getLocation(context);
		if (location == null) {
			return false;
		}

		Address address = location.getAddress();
		if (address == null) {
			return false;
		}

		Listing listing = program.getListing();
		CodeUnit cu = listing.getCodeUnitContaining(address);
		if (cu == null) {
			return false;
		}

		return true;
	}
Only shows addresses to the code unit at the address for the current context.  This differs
from the normal 'find references' action in that it will find references by inspecting 
context for more information, potentially searching for more than just direct references to 
the code unit at the current address.
Ghidra/Features/Base/src/main/java/ghidra/app/actions/AbstractFindReferencesToAddressAction.java