Good evening Heather and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
I would love to help you with this topic.
To answer your question, by default, the iCal export button will only export the built-in fields.
But the good news is that it is possible to customize that functionality with some template customization. You might want to read our Themer’s guide to get a general sense of how that works.
Just to set expectations, as you might know, the scope of our support is mostly to get our wonderful customers started on the right track to customize their site and to help them in case of issues. We unfortunately do not provide complete support for customization.
With that in mind, would you mind sharing an example of what you added and you would want to include in iCal export ?
Best regards,
Geoff B.