I want to use the addOfflineDonation method with the Open API to record offline donations. I see that you can reference custom donation element fields in the standard donate method, can these also be used in the addOfflineDonation method?
Yes, you can use custom donation form fields in the same way you would with the donate method. Take the name of your custom donation form element and make it all lowercase, then replace any special characters or spaces with an underscore. This can be used as your parameter in the API call.