@Marnie56
You can not add tracking info to those URL's, because it is not supported. If you do so , most likely the URL will not resolve at all (being invalid). Also tracking info must be processed on the server side, for example to create some statistics or overview, otherwise it is useless.
If you own a private website,you could create a tracking system yourself by rerouting custom URL's to Airbnb URL's and process the tracking parameters to create a report on that website