Field Names
Switches between showing fields as field names or field values. When enabled the field names are displayed, and when disabled the field values are displayed. Some field contents cannot be displayed.
To change the default field display to field names instead of the field contents, choose - LibreOffice Writer - View, and then select the Field codes check box in the Display area.
When you print a document with enabled, you are prompted to include the field names in the print out.