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