This is to create a dashlet - hence links do make sense!
I know how to add a column to an existing template and create a new report template from scratch.
In each case my limitation is that I am reliant on database fields.
In the dashlet template that comes with CiviCRM I see this:
But I don't know how to use this in a report.
I am editing a copy of the Activity Report template (safely copied to my custom php folder)