When activated, the Cursor tool allows you to see the pointer of your mouse with a crosshair on the output, so that you can know where it is without looking at your screen. That way, you can draw while looking directly at the projection.
Displaying the Cursor
This tool can be toggled ON and OFF with the crosshair icon
in the toolbar.
Customizing the Cursor
You can alter the appearance of the Cursor in Edit → Preferences... → Output → Cursor.
By default, the cursor is white, but you can change its color, as well as its thickness and opacity.