reg number: 2560086, How to set a dynamic value in a combo box?

http://webix.com/snippet/4329e145 . In the snippet pasted here, I have a combo with options list and a default value to display. But, When I click on the combo drop-down, I am trying to set a new value ‘Test 4’ in the combo, which is not working. How do I achieve this?

This is the expected behavior, combo doesn’t allow to set a value that doesn’t exist in the combo list.