Thanks for the quick response. In terms of where the feature/plugin is implemented I suspect it depends on which side of the fence you are.
I have been using yEd for a number of years, but Xcode for just 9 months. When I did a search for Xcode/objective-c to yEd I stumbled on a competitor of yEd, OmniGraffle (albeit paid), which prompted me to post this question.