I found nothing really relevant on the subject, so I am starting a new discussion topic here, though I would be very surprised that the subject has not already been addressed long ago.
Under Quiz administration/ Results/ Grades, a chart of Participants vs Grades is displayed, called 'Overall number of students achieving grade ranges'. Some refered to it as the Quiz attempt chart.
In my opinion, this type of chart is essential to understand the results of a quiz. But it is also essential for other results, e.g. assignments, lessons, category totals and the course total. Yet I have not found how to get these charts, not with the basic Moodle options nor with any plugin. I may have missed how to do this.
Of course, I willthe numerical results and make my own charts. It is not too difficult for example using Excel pivot tables.
However, it would seem to me pretty basic for a software such as Moodle to provide users with a bar chart for each gradebook item and category total as well as for the overall course total, not just for the quizzes.