Some fields such as name, id and description are available in all trackers, making it easy to access their values using the ${items.description} expression.

Custom fields, however, are more difficult to access. In the image below, a custom field named Module is defined in the tracker and is stored in the customField(0) property (only visible when the Show property name checkbox is selected). Therefore, the ${items.getCustomField(0)} expression could be used in the Excel template to access the value of Module, but would also limit the reusability of the template in the scenario where the Module field is stored in different physical properties in different trackers.

For this reason, it is better to access fields using their label as the expression. For example, using ${fields.getByLabel(items,"Module")} will find the field that has a label of Module on an item, and will return the field's value; this makes reusing templates much easier.