Xcode has plenty of documentation, both first-party and third-party. However, I have yet to really find anything that really explains how you are supposed to use a particular part of it, rather than just instructions on what it can do. Xcode is one of those IDEs that is pretty smooth to use if you go with how it’s “supposed” to work and if you don’t it’s extremely rough, and there’s really no good, comprehensive guide that tells you how to do this. My best advice for you would be to watch various WWDC videos about the part you want to work on, where you’ll watch Apple engineers use it on stage. They’ll usually teach you a few things about the “logic” behind it and you’ll be able to use it productively after that.