This is an editable general purpose field that can be drag-dropped into the template's Workspace and defined as to its Attributes, Style, text Input options (if applicable), Lists utilization (if applicable),  Security - Access and Protection through the use of the Inspector.  The default data type is Text of 40 characters Maximum.

Adding Data fields as Local or Linked fields to the Template
Data fields can be brought into a template in one of three ways:

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Table of Contents
Global Template - Topics of Interest
Subledger Template - Topics of Interest
Transaction Template - Topics of Interest
Linked fields explained