On a Transaction Saved Search when we use Name in the Available Filters tab, the list shows all entity records such as Customers, Vendors and Employees.
The reason why the Name field when added as an Available Filter on a Transaction Search shows a dropdown list of all Entity records is because the Name field is used on all kinds of Transaction Searches and is defined by the NetSuite logic.
Example: Name filtered on a Bill Saved Search should show the Vendor Name while Name filtered on a Customer Invoice Search should show the Customer Name.
To work around this, use join field Vendor Fields… > Select Name/ID when working with Vendor related Saved Searches or Customer Fields… > Select Name/ID when working with Customer related Saved Searches as an Available Filter field.
Note: This join field does not contain list of values (dropdown).