Create a Custom Field on the Customer Record that Filters Contacts based on Partners

Contacts will be filtered based on the Company field on the Contact record. Contacts that are just linked to Partners will not display as a possible option in the Contact field dropdown.  

User created a custom field for contacts. Field should be filtered base on Partner selected in the Customer record. Setup of the custom entity field:

• Type: List/Record
• List/Record: Contact
• Applies To tab: Customer

To filter the Contacts in the custom field base on the Partner selected, perform the following steps:

     1. Navigate to Customization > Lists, Records, & Fields > Entity Fields.
     
     2. Edit the custom field.
     
     3. Click the Sourcing & Filtering tab.
     
     4. In the Source List field, select Partner.
     
     5. In the Source Filter By field, select Parent (Partner).
     
     6. Click Save.