Hi,
QC might be part of the optional Graphics Tools for Xcode apps, which can also be accessed from Open Developer Tool menu item in Xcode.
FWIW, Apple seems to have forgotten it exists. It keeps getting more and more difficult to find.
Meanwhile, Xcode continues to get more 'overhauls' by people who have clearly never used any of the competing development tools, or anything on the market for the past 20 years. Yeah that sounds harsh, but Apple developers honestly should expect more from what used to be the leading UI company on the planet.
Where is our visual, node-based dev environment? It could be here by now, if Apple had decided to make it so. Instead, we get this other stuff.
-Chilton the Ancient.