The editable mode that now offers dynamic filtering as you type in the field has a user unfriendly issue.
The dynamic filtering of the combo box items as you type is okay. But once an item has been selected, the "filtering state" of the combo box stays, resulting in having only the selected item displayed in the combo box. All items of the combo box should be displayed once a valid selection has been made, otherwise you need to clear out the field in order to have all your items displayed and selectable again.
This is especially obvious when, for instance, you configure your Extensible Choice as Editable, with the Default Choice as the Top Most Value. The result is that your combo box is shown with the top most item, but with absolutely no way to make a selection, as if the combo box only had the top most item available. It took me quite a few minutes to realize that I had to clear the field, which is not the most user friendly or obvious way of interacting with the combo box.