How to get the single "App" for debugging SwiftUI

Sometimes when an new, unexpected error, hang or deadlock occurs during testing, one might want to stop the app in the debugger and poke around. To do this, in a AppKit app, one would ask for the singleton [NSApplication sharedApplication] by that symbol or the NSApp convenience, and then from there drill down into the app delegate, windows, documents, or whatever was interesting.

How do I do that in a SwiftUI app which is based on App? Apparently, there is a single MyApp:App struct. How can I get the debugger on it and get its properties?