I'm not sure what this is called and have not had much success searching for it yet. In a plugin settings page, I would like a 'combo box' or 'drop down box' that also includes the ability to add an option that is not currently included. That newly added option would be added to the options in the box from that point on.
Is there such a function within the Settings API or does it need a separate text box that is then added to the options array?
Or a better way altogether?