Главная страница у вас может выглядеть следующим образом:

namespace NavigationApp
{
    public partial class MainPage : ContentPage
    {
        Label stackLabel;

        public MainPage()
        {
            Title = "Main Page";
            Button forwardButton = new Button { Text = "Перейти к Page2" };
            forwardButton.Clicked += GoToPage2;

            stackLabel = new Label { Text = "Navigation Stack:" };

            Content = new StackLayout
            {
                Children = { forwardButton, stackLabel }
            };
        }

        protected override void OnAppearing()
        {
            base.OnAppearing();
            DisplayStack();
        }

        private void DisplayStack()
        {
            var navPage = (NavigationPage)App.Current.MainPage;
            stackLabel.Text = $"Стек навигации:\n";

            foreach (Page page in navPage.Navigation.NavigationStack)
            {
                stackLabel.Text += $"{page.Title}\n";
            }
        }

        private async void GoToPage2(object sender, EventArgs e)
        {
            await Navigation.PushAsync(new Page2());
        }
    }
}