Refer to Navigator.of(rootNavigator) in Cupertino tab widgets (#19130)

packages/flutter/lib/src/cupertino/tab_scaffold.dart

@@ -71,6 +71,11 @@ import 'bottom_tab_bar.dart';
 /// )
 /// ```
 ///
+/// To push a route above all tabs instead of inside the currently selected one
+/// (such as when showing a dialog on top of this scaffold), use
+/// `Navigator.of(rootNavigator: true)` from inside the [BuildContext] of a
+/// [CupertinoTabView].
+///
 /// See also:
 ///
 ///  * [CupertinoTabBar], the bottom tab bar inserted in the scaffold.

packages/flutter/lib/src/cupertino/tab_view.dart

@@ -28,6 +28,10 @@ import 'route.dart';
 /// These navigation properties are not shared with any sibling [CupertinoTabView]
 /// nor any ancestor or descendant [Navigator] instances.
 ///
+/// To push a route above this [CupertinoTabView] instead of inside it (such
+/// as when showing a dialog on top of all tabs), use
+/// `Navigator.of(rootNavigator: true)`.
+///
 /// See also:
 ///
 ///  * [CupertinoTabScaffold], a typical host that supports switching between tabs.