What CS told you was incorrect. Surprise, surprise. 😞
You should be able to add promotions on your calendar.
Go to your calendar on the browser version of Airbnb. Don’t select any dates. On the right-hand side, make sure you are on the Pricing tab. There should be a Promotions section, and then Custom Promotion under that. Select Custom Promotion, and it will prompt you to select the dates for the promotion.
NOTE: If you don’t see the Custom Promotion section, there are certain exceptions in which it will be disabled. Read here:
https://www.airbnb.com/help/article/2720
