One field, multiple values added by user

Is there a field type that allows a user to enter a value, and it builds a list of those values... and they can delete values. It'd be like a Dropdown field, or even Query Dropdown, but how would that tie in with a user-built list?

Or would this be two fields working together: use a text field for entry, Auto Actions to take that entry and populate a second Query Dropdown?

Use case: a user wants to add a list of airports they've visited. Rather than just a text area that they list them one line at a time, I'd prefer to enter them as data items so they would be listed as a bullet list. A selected line item could also be removed.

The data entered is actually the airport code (an international standard code from ICAO), so there may be a Query Validation at some point, or they enter a code ("KMSP"), and it pulls the value ("Minneapolis/St. Paul International") from another list. Then, that specific value is added to their list of visited airports.

This would also be used to search users who have visited a specific airport. And may eventually link up with a GroupJive with the same code.

Is there a field type that allows a user to enter a value, and it builds a list of those values... and they can delete values. It'd be like a Dropdown field, or even Query Dropdown, but how would that tie in with a user-built list?

Nope. Sounds like a Tag fieldtype though, which is planned in a later release and will likely be an extension of the existing select fieldtypes. Added a feature ticket for this so we don't forget about it.

forge.joomlapolis.com/issues/7027

Or would this be two fields working together: use a text field for entry, Auto Actions to take that entry and populate a second Query Dropdown?

I suppose that's possible. You could move the value of the text field to a separate database table using CB Auto Actions and its Query action then query for those options using CB Query Field. Not sure how you'd go about removing entries though.