Displaying the related contacts related list and adding the direct field will allow users to distinguish between contacts and related contacts. The related contacts related list shows all contacts that are related to an account, either directly or indirectly. The direct field indicates whether a contact is directly associated with an account or not. By adding this field to the related list, users can easily see which contacts are direct and which are not.
References: https://help.salesforce.com/s/articleView?id=sf.contacts_multiple_accounts.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.contacts_multiple_accounts_direct_field.htm&type=5