In the list of items in the library, the flagged items now have an orange star in the second-last column from the right. The orange star is used to flag an item or items to which you wish to draw a special attention, whether they are favourite items or items to complete or check.
From the list of items, you can click on the star next to an item to flag or unflag the item.
NOTE : When an item's form is displayed, you can move the cursor over the gear icon in the top right of the form and click on Flag. When you are creating a quiz, it is also possible to flag an item (see).