This example illustrates how to customize captions in the "Insert Merge Field" menu. In particular, it shows how to sort them, remove unnecessary items and modify their display text (see the image below). It should be especially noted that the capability to customize actual field names in the document (not only in the context menu for inserting merge fields from the datasource) is not supported in the current version. However, we have a similar suggestion in our database: Add mapped field support in the MailMerge mechanism. Please track it to be informed on our progress with this item.