XpressDox uses XSLT technology to insert data elements into Merge Fields. This means that a vast amount of functionality is available to the experienced user, especially the XSLT functions, which are used to format data. XpressDox functions and XSLT functions can be mixed in one Merge Field
Use Google to find help fast. For example, search on "xpressdox choosefromlist".
The background to this command probably needs a bit of experience in authoring more complex templates. Because XpressDox uses XSLT technology to format the documents, it is possible to use XSLT and XPath expressions to control some of the processing.