You may try to add another UXMenuBar as the sub-menu as shown in the following snippet code.

<Intersoft:UXMenuBar x:Name="MenuBar1" OpenSubMenuOnMouseOver="True" >
    <Intersoft:UXMenuItem Header="_Menu1">
        <Intersoft:UXMenuBar>
            <Intersoft:UXMenuItem Header="_SubMenu1" />
            <Intersoft:UXMenuItem Header="SubM_enu2" />
	</Intersoft:UXMenuBar>
    </Intersoft:UXMenuItem>
    <Intersoft:UXMenuItem Header="_Menu2">
        <Intersoft:UXMenuBar>
            <Intersoft:UXMenuItem Header="_SubMenu3" />
            <Intersoft:UXMenuItem Header="SubM_enu4" />
        </Intersoft:UXMenuBar>
    </Intersoft:UXMenuItem>
</Intersoft:UXMenuBar>

The result looks like the following screenshot.

Please let us know whether this helps or not.

Yudi, yes this is what I`m looking for instead of one thing, I need to bind it from MVVM collection, in this case MenuItems may not be presented declaratively.

I have an idea to load the menu items on demand (maybe by utilizing SelectedItem property) and put the child UXMenuBar as DataTemplate. However, I will need more time to test the feasibility of this.

I will get back to you with the result as soon as possible.