AFX allows you to add, modify, or remove runways, taxiways, and paths, taxiway signs, aprons, start location, navaids, parking spots and many more airport features. You can also modify your aircraft config by adding,
atc_parking_codes=UAL
atc_parking_codes=GATE I know that Fsdt airports will then park your aircraft at or near the correct terminal. Gates can be changed to Cargo as well.