Add a disabled/ non-selectable separator in a bound ComboBox - visual-c++

Question

I have a ComboBox and I want to add a separator which is disabled, non-selectable.
Standard functions such as add, edit, delete should be selectable under the separator.
The items containing an image and text should be displayed above the separator.
<ComboBox Name="cmbTest">
<!--These items should be loaded by code or ViewModel.-->
<ComboBoxItem >Item1</ComboBoxItem>
<ComboBoxItem >Item2</ComboBoxItem>
<ComboBoxItem >Item3</ComboBoxItem>
<!--Separator which is disabled.-->
<ComboBoxItem IsEnabled="False" >
<NavigationViewItemSeparator BorderThickness="1"></NavigationViewItemSeparator>
</ComboBoxItem>
<!--Menu below the separator.-->
<ComboBoxItem x:Name="cmbiNewApplication">Neu</ComboBoxItem>
<ComboBoxItem x:Name="cmbiEdit">Bearbeiten</ComboBoxItem>
<ComboBoxItem x:Name="cmbiDelete">Löschen</ComboBoxItem>
<ComboBoxItem x:Name="cmbiImportApplication">Import</ComboBoxItem>
<ComboBoxItem x:Name="cmbiExportApplication" >Export</ComboBoxItem>
</ComboBox>
Currently, my ComboBox is tied to a ViewModel and I've created a TemplateSelector on advice. Unfortunately, the ComboBoxItem in the template doesn't seem to be the generated ComboBoxItem itself, so the IsEnabled property has no effect.
<ComboBox x:Name="cmbApplication"
CornerRadius="3"
Width="300"
ItemsSource="{x:Bind AppProcessMainViewModel.AppProcesses}"
Tapped="cmbApplication_Tapped" >
<ComboBox.ItemTemplateSelector>
<local:MenuDataTemplateSelector>
<local:MenuDataTemplateSelector.DefaultTemplate>
<DataTemplate x:DataType="local:AppProcess" >
<StackPanel Orientation="Horizontal">
<StackPanel Orientation="Horizontal" Opacity="{x:Bind BoolToOpacity(Activated), Mode=OneWay}">
<TextBlock Text="{x:Bind Description, Mode=OneWay}"></TextBlock>
</StackPanel>
</StackPanel>
</DataTemplate>
</local:MenuDataTemplateSelector.DefaultTemplate>
<local:MenuDataTemplateSelector.MenuTemplate>
<DataTemplate x:DataType="local:AppProcess">
<ComboBoxItem IsEnabled="False" Height="22" >
<NavigationViewItemSeparator BorderThickness="1"></NavigationViewItemSeparator>
</ComboBoxItem>
</DataTemplate>
</local:MenuDataTemplateSelector.MenuTemplate>
</local:MenuDataTemplateSelector>
</ComboBox.ItemTemplateSelector>
</ComboBox>
My consideration was that I set the IsEnabled property of the item in the Tapped event of the combo box.
Unfortunately, I really can't figure out how to get the property of the ComboBoxItem by index.
How can I set the property?
Is this really the best approach (TemplateSelector and setting the property in the Tapped event)?
I've already read a lot about this and unfortunately there seems to be a lot missing in WinUI 3 in contrast to UWP/WPF that make things much easier.
I'm trying to get the item via the index and cast it, but there seems to be another problem, maybe because of the ViewModel?
Something like...
//Error
auto cb = cmbApplication().Items().GetAt(1).as<winrt::Microsoft::UI::Xaml::Controls::ComboBoxItem>();

Answer 1

I came across this site of the MS documentation (Find DataTemplate Generated Elements) and just tried it out, which works wonderfully... happy new year!
auto item = cmbApplication().ItemContainerGenerator().ContainerFromItem(cmbApplication().Items().GetAt(3));
item.as< winrt::Microsoft::UI::Xaml::Controls::ComboBoxItem>().IsEnabled(false);