set select2 value code example
Example 1: jquery to set value in select2 dropdown button
$("#u20_cre").select2().val(["1","6"]).trigger("change");
Example 2: select2 dropdown with option to add new item
$('#select2')
.select2()
.on('select2:open', () => {
$(".select2-results:not(:has(a))").append('<a href="#" style="padding: 6px;height: 20px;display: inline-table;">Create new item</a>');
})