Setting combobox value from code?

I just updated the UI library for a project to the 1.8.4 and am now trying to make use of the new autocomplete/combobox feature. I have this working fine, but need to dynamically set the value of the combobox when populating an edit form. I've tried setting the value on the original select and that is not working.

I'm sure I can determine the selector for the dynamically created input box and set the value there, but is this the "right" way to do things?

Thanks