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I am not sure what exactly you are trying to achieve. By default each item element has a particular value element. The different types of properties have different item elements and you cannot use the same item element with different kind of value elements - you should change the entire item element. Complete example for this is available here: Custom items
If you need further assistance with this please send us your code. This will give is better understanding of your exact scenario and we will be able to provide you with a proper solution.
I hope this helps.
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