If the pinball game you're using has the feature, if you can't map the trackball to it, you could always use a program similar to joy2keys to do it. In real pinball, you shake the machine while holding the sides, but you'll have to take a hand off to reach for the trackball with your method. Perhaps you could set your secondary pinball left/right buttons as shifted buttons. If you press them by themselves, they nudge left or right, but if hold either of them and hit the mains, they nudge up. Something like that.
Just thinking out loud and typing what comes out...