When presenting or sharing your screen,
1. Press a CMD_1 to zoom in the entire screen.
2. When zoomed in, draw with your touchpad or mouse using the drag gesture.
3. Hit ESC to go back to where you were.
Other things to know,
a) You can configure the shortcut from the dock menu
b) You can access the help anytime from the dock
点击按钮跳转至开发者官方下载地址...