The Code field is used as a reference for calculation
formulas. You can specify an alphanumeric identifier, or Code, for any row in
your Lines Definition and use it for any formulas that need to reference this
line. Your Code field can reference the Natural account or it can be a unique
value you specify, such as an identifier for a summary or calculation
line.
The Code field value must be unique within the given Lines Definition, but different Lines Definitions can re-use the same values.
Also see the section on the Line Definition Properties Pane Option Section for the Display Code option.