In the list of quizzes in the library, the flagged quizzes now have an orange star in the second-last column. An orange star is used to flag a quiz or quizzes to which you want to draw a special attention. It could be a quiz to complete or check.
It is possible to flag or to unflag a quiz by clicking on the star next to the appropriate quiz title in the list of quizzes.
NOTE: When a quiz's form is displayed, you can move the cursor over the gear icon in the top right of the form and click on Flag.