NavigationBarTitle.swift

import SwiftUI

struct Child: View {
    var body: some View {
        ScrollView(.vertical, showsIndicators: true) {
            ForEach(1...100, id: \.self) {
                Text("#\($0) Hello, world!")
                    .padding()
            }
        }
            .navigationTitle(Text("Child Title"))
//            .navigationBarTitle(Text("Child Title"))
            .navigationBarTitleDisplayMode(.inline)
//            .toolbar {
//                ToolbarItem(placement: .principal) {
//                    Text("Child TItle")
//                }
//            }
    }
}

struct ContentView: View {
    var body: some View {
        NavigationView {
            ScrollView(.vertical, showsIndicators: true) {
                ForEach(1...100, id: \.self) {
                    Text("#\($0) Hello, world!")
                        .padding()
                }
            }
            .navigationTitle(Text("Parent Title"))
//                .navigationBarTitle(Text("Parent Title"))
            .toolbar {
//                    ToolbarItem(placement: .principal) {
//                        Text("Parent Title")
//                    }
                ToolbarItem(placement: .automatic) {
                    NavigationLink("Go", destination: Child())
                }
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}