what is displayed is a compute string which is an XPath expression used to construct a string representing a record in a table associated with the schema. Compute string is mainly used in the graphical interface to display the label of a selected record.
The Compute string is defined via the <compute-string> element under the main element of the data schema. An expr attribute contains an XPath expression to calculate the display.
That being said, you can find the url type under trackingUrl link (screenshot below)