When moving automation using this technique, you’ll sometimes find yourself accidentally moving the automation to the right and left. It’s nice that this is possible, but aggrivating when it’s not what you mean to do.
To confine movement to up and down only, hold down Cmd(Mac) / Ctrl (PC) while dragging.
Option/Alt is also used to confine motion, but works slightly differently. If you find that you’ve accidentally dragged your automation off to one side, hit Option and as soon as you move the mouse, you’ll see it snap back to it’s original horizontal position. Cmd, on the other hand, can be used to confine the motion to any position you want. In other words, you could drag the automation off to the side a little bit, then hold down Cmd to confine the motion at the new point.