I need to pass the booking id or any other reference object to a custom event in my SRM implementation. I can add the event to the Booking Manager' Events table, but I'm not sure what is the required syntax to make this information available at the script's execution time.
Gelber Mahecha [SLC] [DevOps Enabler] Selected answer as best 28th August 2020
Indeed, the Config >> Events page on the Booking Manager allows you to add any custom event that should be executed during, or even outside the window of the bookings.
Into the configuration of the custom event, the placeholder [RESERVATIONGUID] can be used, which will automatically be translated into ID of the corresponding booking on execution.
Example below on how this can be achieved. 
Gelber Mahecha [SLC] [DevOps Enabler] Selected answer as best 28th August 2020