How to use NavigationView in a DocumentGroup on iPad

You might need to fallback to using the old UIKit App Delegate life cycle type instead of the newer DocumentGroup. With the old pattern, you are totally responsible for presenting the document view after the user selects a document. That gives you more control. With DocumentGroup, you only provide your content which DocumentGroup then embeds in it’s own view hierarchy. I have found that DocumentGroup doesn’t provide all the flexibility that was previously available. I’m hoping it will in the future, but for now, I’m avoiding it.

Using Reference File Document Group followed by NavigationView I've been able to have a document group that open a navigation view, which have the sidebar.
Here an extract:

Code Block 
import SwiftUI
@main
struct MyApp: App
{
	var body: some Scene
	{
		DocumentGroup(newDocument:
						{ () -> myDocumentClass in	// Create a new document
							return myDocumentClass()
						},
					  editor:
						{ (file: ReferenceFileDocumentConfiguration<myDocumentClass>) -> ContentView in
							return ContentView()
						}
		)
	}
}
class myDocumentClass: ReferenceFileDocument
{
	typealias Snapshot = ContentView
	var myData: Snapshot
	...
}
struct ContentView: View 
{
	var body: some View
	{
		NavigationView
		{
			sideBar()
			mainView()
		}
		.navigationViewStyle(DoubleColumnNavigationViewStyle())
	}
}