Hi luoy,
Any news from the developers? As you will see in the other posts I listed, a lot of people are looking for that feature, and implementing it would really take WP types to the next level. For developers who know the code this should really be easy (as explained earlier, the API calls are already there, it's just about adding a bit of HTML to create a dropdown list). If you guys haven't decided on how the UI should look like, I would strongly recommend using a combobox as it makes it easy to make a choice when many values are available. See:
https://jqueryui.com/resources/demos/autocomplete/combobox.html
Please guys, do yourself a favor and implement that feature, it will have a big positive impact for your customers.
Regards,
Max