Course reports

A course report plugin is just another folder inside course/report/

If there is a mod.html file inside there, it will be included with the others when you visit course/report.php?id={courseid} in your browser.

That HTML fragment can do anything you like. A common thing is to include a link to course/report/myreport/index.php. That's all it is, simple, and gives you almost unlimited flexibility.