Score sharing is so helpful during a lesson, and we understand that marking on the score is helpful, too.
At this time, Forte does not have a whiteboard feature where you can write on a score that is being shared.
However, you can share your screen to share your score and make any changes or annotations directly in the application that you are using to display your score (Preview, Adobe, forScore, etc.).
Every marking or change you make on your computer is automatically reflected to your student/teacher in real-time. They see what you see!