The generated-content-marker attribute in the wizard group is the flag that turns a normal report into a template. This attribute can only be applied to a band (group header, group footer, details header, details footer, details, or sub-band).
RDW will insert its auto-generated content into the first band with the generated-content-marker set to true. This applies to the group header, group footer, details header, details footer, and the details bands. In the event there are more groups defined in the Report Design Wizard than defined in the template, it repeats the last defined group header and footer in the template.