When the feature for Contacts to multiple Accounts is enabled, a Contact can have a direct relationship with multiple Accounts. However, one of these relationships must be designated as the primary Account relationship. This relationship is required on a Contact regardless of the page layout settings and cannot be removed unless the Contact is deleted or merged with another Contact. References: https://help.salesforce.com/s/articleView?id=sf.shared_contacts_set_up.htm &type=5 https://help.salesforce.com/s/articleView?id=sf.shared_contacts_considerations.htm &type=5