Symptoms

Reference field on table shows sys_id instead on Display value for the table

Release

All Supported

The reference lists use the "sys_ref_list" view and it needs to be configured to show the correct columns.

Navigate to System UI > Views.
Search and select sys_ref_list
In the "List" related list, search for the table you are referencing and open the record
Go to related lists and locate the "List Elements" related list
The elements are the columns that are displayed on the list when you click on the reference icon. You will need to add/remove as desired
To add the desired column to the list, click new or edit an existing record
The "Element" field value should be set to the name of the desired field. For example, if you are referencing sys_user table, you can set the user_name field as one of the columns.