Hi Pollyanna, yes there is a quick way to mark your lessons.
If you're in the Play Courses screen:
1. Right-click on the yellow "Day ## Lessons" bar and select "Mark Played"
2. Or right-click on "Session 1," "Session 2," or any of the Word Flash / Multisensory / Picture Flash labels then select "Mark Played"
If you prefer to mark several lessons at a time, it's best to do it from the Advanced Play/Edit screen:
1. In the Advanced Play/Edit screen, go to Courses and select the semester you want to mark
2. Highlight all the lessons / folders you've played before -- press and hold Shift while clicking on the first folder in the list and the last folder you've played
3. Right-click on your selection and select "Mark Played"