Thanks for the details, I now see your problem. The PanelBar is a hierarchical ItemsControl, so each item in its ItemsSource will be dynamically wrapped in a PanelBarItem. The rendering of your business objects is determined by the DataTemplate you specify. The key point here is that the content of each data item will be rendered in the header
of the dynamically created PanelBarItem that wraps it. This is because the control is hierarchical in nature and its items have some content (rendered in an item's header) and a set of subitems (rendered as such below the header). From your explanation I see that you want to have the ellipses from your custom UserControl to be rendered below a PanelBarItem's header. However, keeping in mind the hierarchical nature of the control, this would require you to transform your current list of items to a hierarchical such. This can be done in several ways, but as you are probably aware by now, this would require some fiddling with the structure of your original data.
I would suggest that you take a look at our OutlookBar
control which is quite similar to the PanelBar, but is not hierarchical and may be more suitable to your scenario. Please consider it and let me know if you want to use it instead of the PanelBar. In case you still want to use the PanelBar, let me know and I will create an example for you.
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