square.onBookingCustomAttributeVisibleDeleted subscribes to booking.custom_attribute.visible.deleted for the selected seller. It does not require an additional Square OAuth permission.
Example
automations/square-on-booking-custom-attribute-visible-deleted.automation.ts
Event
A custom attribute that’s visible to your application was deleted from a booking. The signal resolves to the officialSquare.BookingCustomAttributeVisibleDeletedEvent payload with type narrowed to booking.custom_attribute.visible.deleted.