Add new bookings to multiple calendars

While checks availability on multiple calendars, new bookings can only be added to a single calendar that you select under Calendar & teams.

To add the booking to multiple calendars, use the Invite participants feature under Notifications > Calendar events. You can invite any email address to bookings received through your booking page. They will receive a calendar invitation. Remove email addresses by clicking the x next to the email. 

"All booking form emails" are the email addresses entered on your booking form, so your booker will also have this event automatically added to their calendar