The Comment tool is an interactive note tool operating between Composer and an unpublished course. You can add and view comments in the Composer section on the right, either per page or per course. Each comment can be assigned a status to make it easier to monitor the comments. Comments can also be edited and deleted afterwards.
When previewing a course, the comment tool opens from the comment tool button in the top bar of the course. Comments are automatically linked to the active page.