Vantage has a built in
.csv importing tool for listings and events, but I'm not clear on where you want the dropdown box to be/what for? If you are referring to a dropdown box on the listing form, specific to the category, you can create
custom forms within Vantage, however there is no bulk import option for these. You simply create the form and apply it to a category/categories. If you were looking to do this in bulk, then you'd likely need knowledge of mysql admin in order to create a script to run this from the database side. If that's not what you meant, please feel free to clarify. Thanks :)