I've answered to the support thread opened on the same subject. I would like to ask you continue our discussion in only one thread to avoid any duplication. Thank you for your understanding.
Here is a quote of the answer:
In general, adding a new item to the data source is not supported by the widget out-of-the-box and implementing and supporting custom modifications falls out of the scope of the entitled support service.
Nevertheless, I reviewed the provided demo and the problem comes from the fact that widget is being filtered (the data is reduced) when the form is re-bound. Hence it will select only the last item. This behavior can be overcome with manual filter cleaning in the widget change event handler:
The modified file is attached to this message.
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