When a questionnaire form is displayed, you can move the cursor over the gear icon in the top right of the form and click on Flag. You can also flag or unflag a questionnaire by clicking on the star next to it in the questionnaire list.
An orange star appears in the last column of the questionnaire list to indicate those that are flagged. This feature is used to let you know that certain questionnaires require further attention, e.g., they need to be reviewed or completed.