Thrid-class navigation need in NavigationViewItem

[MatinxHT]

Is your feature request related to a problem? Please describe

In CommunityToolkit MVVM Toolkit Sample App the NavigationViewItemGroup could set a new NavigationViewItemGroup inside.But now WPF-UI still oldfasion way of which "group-item"

Describe the solution you'd like

It's good to see if the NavigationViewItem MenuItemsSource can set a new MenuItemsSource as an NavigationViewItem

Describe alternatives you've considered

And I am trying my best to code an WPF CommunityToolkit MVVM Toolkit Sample App !

Additional context

No response

[MatinxHT]

The enthusiasm has faded