You can define custom fields which collect data for each person in a booking.
Create Configuration Items with names: GUEST_CUSTOM1, GUEST_CUSTOM2, …
In the above example, a field will be added to the Booking screens to collect a mobile phone number for each person in the booking . “Mobile” will be the placeholder.
You can’t delete Configuration Items once they are created, but leaving the “value” field blank will mean the entry is ignored.