Thanks to Kelly's Answer i also added a Layer select control ,below is the code (see the Kelly's Answer for more detail)
function _createTemplateFilter()
{
widget._origGetItemsFromLayerFunc = widget._getItemsFromLayer;
widget._getItemsFromLayer = lang.hitch(this, function () {
var items;
items = widget._origGetItemsFromLayerFunc.apply(templatePicker, arguments);
items = arrayUtils.filter(items,(item) => (item.layer.layerId == select.value));
return items;
});
}