Proof-of-concept for swapping out items in a navigation path in SwiftUI, see https://mastodon.social/@caseyliss/110103718721678762

ContentView.swift

import SwiftUI

enum NavDest: Hashable {
    case a
    case b
    case c
    case d(Int)
}

struct ContentView: View {
    @State var navPath: [NavDest] = []

    var body: some View {
        NavigationStack(path: $navPath) {
            VStack {
                Image(systemName: "globe")
                    .imageScale(.large)
                    .foregroundColor(.accentColor)

                Text("Hello, world!")
                    .padding(.bottom)

                Button {
                    navPath.append(.a)
                } label: {
                    Label("Push A", systemImage: "a.circle")
                }
            }
            .padding()
            .navigationDestination(for: NavDest.self) { dest in
                switch dest {
                case .a:
                    Button {
                        navPath.append(.b)
                    } label: {
                        Label("Push B", systemImage: "b.circle")
                    }
                    .buttonStyle(.borderedProminent)
                    .navigationTitle("A")

                case .b:
                    Button {
                        navPath.append(.c)
                    } label: {
                        Label("Push C", systemImage: "c.circle")
                    }
                    .buttonStyle(.borderedProminent)
                    .navigationTitle("B")

                case .c:
                    Button {
                        navPath.append(.d(1))
                    } label: {
                        Label("Push D(1)", systemImage: "d.circle")
                    }
                    .buttonStyle(.borderedProminent)
                    .navigationTitle("C")

                case let .d(n):
                    HStack {
                        Button {
                            navPath[navPath.count - 1] = .d(n - 1)
                        } label: {
                            Label("Swap in D(\(n - 1))", systemImage: "arrow.down.circle")
                        }
                        .buttonStyle(.borderedProminent)

                        Button {
                            navPath[navPath.count - 1] = .d(n + 1)
                        } label: {
                            Label("Swap in D(\(n + 1))", systemImage: "arrow.up.circle")
                        }
                        .buttonStyle(.borderedProminent)
                    }
                    .navigationTitle("D(\(n))")
                }
            }
        }
    }
}

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

NavigationPathStuffApp.swift

import SwiftUI

@main
struct NavigationPathStuffApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
                .buttonStyle(.borderedProminent)
        }
    }
}