For scrolling to the right:
New event - System - compare. So then you can compare the two values: "Get mouse X" and "Get X right of visible screen". Which will check if the mouse is on the right edge of the screen.
action - system - scroll to X. Then you want to retrieve the current "Get scroll X" then add 10 to it.
and you'll end up with this:
however I made it so that if your mouse is within 10 pixels of the right edge, by checking if the mouse is greater than right edge -10 pixels - because it's too annoying to try and get the mouse to exactly the right edge.