How do I change a customer's details on a booking?

In the sidebar, open Orders and find the order concerned. You can type the customer name or email straight into the search field.

Open the order: the Customer card sits in the right-hand panel.

Click the pencil icon at the top right of that card to change the name, the email address, the phone number or the address, then save.

The details asked of each participant are edited separately, in the booking detail, under Contacts.