Form & View Settings
A field of the DocType which will be displayed as a title in the Form
Set the title field
Enter the name of a custom field in 'Title Field'
Show Title in Link Fields
You can enable Show Title in Link Fields to display Title instead of Name in the Link Fields in another doctype.
So if a custom field of 'link' type is added in another doctype (or through customize form), then the title of the linked document will be displayed in the field instead of name.