The HamburgerMenu control uses the HamburgerMenuListBox control to show the menu items. You can use a DataTemplate with an Expander control with an HamburgerMenuListBox control as the Child to show submenu items:

[montanarispark]

          The HamburgerMenu control uses the HamburgerMenuListBox control to show the menu items. You can use a DataTemplate with an Expander control with an HamburgerMenuListBox control  as the Child to show submenu items:

            <DataTemplate DataType="{x:Type mah:HamburgerMenuIconItem}">
                <Expander x:Name="ExpanderPart"
                          HorizontalAlignment="Stretch"
                          HorizontalContentAlignment="Stretch"
                          BorderThickness="0"
                          FlowDirection="RightToLeft"
                          mah:HeaderedControlHelper.HeaderBackground="Transparent"
                          mah:HeaderedControlHelper.HeaderForeground="{Binding RelativeSource={RelativeSource AncestorType={x:Type mah:HamburgerMenu}}, Path=PaneForeground}"
                >
                    <Expander.Header>
                        <DockPanel Height="48" LastChildFill="True" Background="Transparent"
                                   FlowDirection="LeftToRight">
                            <ContentControl x:Name="IconPart"
                                            Width="{Binding RelativeSource={RelativeSource AncestorType={x:Type mah:HamburgerMenu}}, Path=CompactPaneLength}"
                                            Content="{Binding Icon}"
                                            DockPanel.Dock="Left"
                                            Focusable="False"
                                            IsTabStop="False">
                            </ContentControl>
                            <TextBlock VerticalAlignment="Center"
                                       FontSize="16"
                                       Text="{Binding Label}" />
                        </DockPanel>
                    </Expander.Header>
                    <mah:HamburgerMenuListBox ItemsSource="{Binding Tag}"
                                                   Margin="0,0,10,0"
                                                   FlowDirection="LeftToRight"
                                                   HorizontalAlignment="Stretch"
                                                   Foreground="{Binding RelativeSource={RelativeSource AncestorType={x:Type mah:HamburgerMenu}}, Path=PaneForeground}"
                                                   IsTextSearchEnabled="True"
                                                   ItemContainerStyleSelector="{StaticResource HamburgerMenuItemStyleSelector}"
                                                   ItemTemplateSelector="{DynamicResource MenuItemTemplateSelector}"
                                                   SelectionMode="Single"
                    />
                </Expander>
            </DataTemplate>

You can then insert the submenu items in the tag property:

        <mah:HamburgerMenu.ItemsSource>
            <mah:HamburgerMenuItemCollection>
                <mah:HamburgerMenuIconItem Label="Account">
                    <mah:HamburgerMenuIconItem.Icon>
                        <iconPacks:PackIconMaterial Width="22"
                                                    Height="22"
                                                    HorizontalAlignment="Center"
                                                    VerticalAlignment="Center"
                                                    Kind="Account"/>
                    </mah:HamburgerMenuIconItem.Icon>
                    <mah:HamburgerMenuIconItem.Tag>
                        <mah:HamburgerMenuItemCollection>
                            <mah:HamburgerMenuIconItem Label="Add">
                                <mah:HamburgerMenuIconItem.Icon>
                                    <iconPacks:PackIconMaterial Width="22"
                                                                Height="22"
                                                                HorizontalAlignment="Center"
                                                                VerticalAlignment="Center"
                                                                Kind="AccountPlus"/>
                                </mah:HamburgerMenuIconItem.Icon>
                            </mah:HamburgerMenuIconItem>
                            <mah:HamburgerMenuIconItem Label="Edit">
                                <mah:HamburgerMenuIconItem.Icon>
                                    <iconPacks:PackIconMaterial Width="22"
                                                                Height="22"
                                                                HorizontalAlignment="Center"
                                                                VerticalAlignment="Center"
                                                                Kind="AccountEdit"/>
                                </mah:HamburgerMenuIconItem.Icon>
                            </mah:HamburgerMenuIconItem>
                        </mah:HamburgerMenuItemCollection>
                    </mah:HamburgerMenuIconItem.Tag>
                </mah:HamburgerMenuIconItem>
            </mah:HamburgerMenuItemCollection>
        </mah:HamburgerMenu.ItemsSource>

This is what the result looks like:

Originally posted by @derSteff18 in #3018 (comment)

I add subItems to the inner HamburgerMenuItemCollection dynamically from code behind. I set the Command for the sub-menu, but it isn't fired if I click the sub-menu. This is my code:

public partial class MainUC : UserControl
{
    public MainUC()
    {
        InitializeComponent();
    }
    private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        LoadPersonalizedTrend();
    }

.
.
.

    private void LoadPersonalizedTrend()
    {
        mnuTrendCollection.Clear();
        HamburgerMenuGlyphItemForTrend mnu = new HamburgerMenuGlyphItemForTrend();
        mnu.IsPersonalizedTrend = true;
        mnu.Label = "Test 1";
        mnu.Glyph = "ChartMultiple";
        mnu.Command = new DelegateCommand(Execute);
        mnuTrendCollection.Add(mnu);
    }

    private void Execute(object o)
    {
        MessageBox.Show("Hello");
    }

}

public class DelegateCommand : ICommand
{
    private readonly Func<object, bool> _canExecute;
    private readonly Action<object> _execute;

    public DelegateCommand(Action<object> execute) : this(execute, s => true)
    {
    }

    public DelegateCommand(Action<object> execute, Func<object, bool> canExecute)
    {
        _execute = execute;
        _canExecute = canExecute;
    }

    public bool CanExecute(object parameter)
    {
        return _canExecute(parameter);
    }

    public void Execute(object parameter)
    {
        _execute(parameter);
    }

    public event EventHandler CanExecuteChanged;
}

If I do the same with a first level menu item it works. Itried also to use the ItemClick event, but it doesn't work for the subitems.

Thanks