feat: Add MainCommandMode.Hidden to completely hide NavigationBar MainCommand

doc/controls/NavigationBar.md

@@ -285,12 +285,23 @@ The height is fixed and cannot be changed.
 
 ### MainCommandMode
 
-The `NavigationBar` has a property named `MainCommandMode` that can be set to either:
+The `NavigationBar` has a property named `MainCommandMode` that can be set to:
 
 1. `MainCommandMode.Back` (default)
-1. `MainCommandMode.Action`
+2. `MainCommandMode.Action`
+3. `MainCommandMode.Hidden`
 
-`MainCommandMode` should be set to `Action` when the `MainCommand` is being used for anything other than backward navigation, such as displaying a burger menu or displaying a prompt to the user before the navigation occurs.
+#### Back Mode (Default)
+
+When set to `Back`, the `MainCommand` will be used for backward navigation. The button will automatically appear when the Frame has items in its back stack and will trigger navigation back when clicked.
+
+#### Action Mode
+
+`MainCommandMode` should be set to `Action` when the `MainCommand` is being used for anything other than backward navigation, such as displaying a burger menu or displaying a prompt to the user before the navigation occurs. In this mode, the `MainCommand` remains visible and its click behavior must be handled by setting the `Command` property or handling the `Click` event.
+
+#### Hidden Mode
+
+When set to `Hidden`, the `MainCommand` will be completely hidden from view regardless of the Frame's back stack state. This is useful when you want to hide the main command entirely, such as on a home/landing page or when implementing custom navigation logic that doesn't require a visible back button.
 
 ### MainCommand
 

src/Uno.Toolkit.RuntimeTests/Tests/NavigationBarTests.cs

@@ -253,6 +253,62 @@ public async Task MainCommand_In_Popup_With_Page_With_BackStack(MainCommandMode
 			}
 		}
 
+		[TestMethod]
+		public async Task MainCommand_Hidden_Mode_Hides_Button()
+		{
+			var mainCommand = new AppBarButton();
+			var navigationBar = new NavigationBar 
+			{ 
+				Content = "Title", 
+				MainCommandMode = MainCommandMode.Hidden, 
+				MainCommand = mainCommand 
+			};
+			var content = new Grid { Children = { navigationBar } };
+
+			await UnitTestUIContentHelperEx.SetContentAndWait(content);
+
+			Assert.AreEqual(Visibility.Collapsed, mainCommand.Visibility, "MainCommand should be collapsed when MainCommandMode is Hidden");
+			Assert.IsFalse(navigationBar.TryPerformMainCommand(), "TryPerformMainCommand should return false when MainCommandMode is Hidden");
+		}
+
+		[TestMethod]
+		public async Task MainCommand_Hidden_Mode_In_Frame_Stays_Hidden()
+		{
+			var frame = new Frame() { Width = 400, Height = 400 };
+			await UnitTestUIContentHelperEx.SetContentAndWait(frame);
+
+			frame.Navigate(typeof(NavBarFirstPage));
+			await UnitTestsUIContentHelper.WaitForIdle();
+
+			var firstPage = frame.Content as NavBarFirstPage;
+			var firstNavBar = firstPage?.FindChild<NavigationBar>();
+
+			if (firstNavBar != null)
+			{
+				firstNavBar.MainCommandMode = MainCommandMode.Hidden;
+				await UnitTestsUIContentHelper.WaitForIdle();
+
+				// Navigate to a second page to create backstack
+				frame.Navigate(typeof(NavBarSecondPage));
+				await UnitTestsUIContentHelper.WaitForIdle();
+
+				var secondPage = frame.Content as NavBarSecondPage;
+				var secondNavBar = secondPage?.FindChild<NavigationBar>();
+
+				if (secondNavBar != null)
+				{
+					secondNavBar.MainCommandMode = MainCommandMode.Hidden;
+					await UnitTestsUIContentHelper.WaitForIdle();
+
+					// Even with backstack, Hidden mode should keep button collapsed
+					Assert.AreEqual(Visibility.Collapsed, secondNavBar.MainCommand?.Visibility, 
+						"MainCommand should remain collapsed in Hidden mode even with backstack");
+					Assert.IsFalse(secondNavBar.TryPerformMainCommand(), 
+						"TryPerformMainCommand should return false in Hidden mode");
+				}
+			}
+		}
+
 #if __ANDROID__ || __IOS__
 		[TestMethod]
 		public async Task NavigationBar_Dynamic_Background()

src/Uno.Toolkit.UI/Controls/NavigationBar/LeftCommandMode.cs

@@ -10,5 +10,6 @@ public enum MainCommandMode
 	{
 		Back,
 		Action,
+		Hidden,
 	}
 }

src/Uno.Toolkit.UI/Controls/NavigationBar/NavigationBar.cs

@@ -97,6 +97,8 @@ protected override void OnApplyTemplate()
 
 		internal bool TryPerformMainCommand()
 		{
+			// Only perform back navigation when MainCommandMode is Back
+			// Action and Hidden modes should not perform automatic navigation
 			if (MainCommandMode != MainCommandMode.Back)
 			{
 				return false;
@@ -198,13 +200,24 @@ private void OnBackStackChanged(object? sender, NotifyCollectionChangedEventArgs
 
 		internal void UpdateMainCommandVisibility()
 		{
+			if (MainCommand is not { } mainCommand)
+			{
+				return;
+			}
+
+			if (MainCommandMode == MainCommandMode.Hidden)
+			{
+				mainCommand.Visibility = Visibility.Collapsed;
+				return;
+			}
+
 			if (MainCommandMode != MainCommandMode.Back)
 			{
 				return;
 			}
 
 			var buttonVisibility = Visibility.Collapsed;
-			if (GetPage() is { } page && MainCommand is { } mainCommand)
+			if (GetPage() is { } page)
 			{
 				if (page.Frame?.CanGoBack ?? false)
 				{