I am begging you, as a teacher that teaches multiple classes each day to add a feature to erase all annotation on all slides with one click. Right now, we have to erase each slide individually and if you have 20 slides, that takes some time. Then, you have to do that 5 times a day if you teach that class over and over. Please, one click to erase all annotation so we can clear with one click and restart the presentation fresh.