square.onMerchantCustomAttributeDefinitionOwnedDeleted subscribes to merchant.custom_attribute_definition.owned.deleted for the selected seller. It requires MERCHANT_PROFILE_READ.
Example
automations/square-on-merchant-custom-attribute-definition-owned-deleted.automation.ts
Event
A custom attribute definition owned by your application was deleted. Note that only the definition owner can delete a custom attribute definition. The signal resolves to the officialSquare.MerchantCustomAttributeDefinitionOwnedDeletedEvent payload with type narrowed to merchant.custom_attribute_definition.owned.deleted.