I added this in StrokesPlus as an application only script, and set the gestures to react to middle mouse button, left and right 'swipe'

Horiz. Scroll (OneNote for example)

// last element in array
var lastGesturePointInArray = action.GesturePoints.Length - 1;

// pixels travelled
var distanceTravelled = action.GesturePoints[lastGesturePointInArray].X - action.GesturePoints[0].X;

// Edit if need be:
var horizScrollDist = 1.5;

// turn to absolute num
if (distanceTravelled < 0) {
    distanceTravelled *= -1;
    horizScrollDist *= -1;
};

horizScrollDist *= distanceTravelled;

//sp.ConsoleLog('\n');
//sp.ConsoleLog(action.GesturePoints[0]);
//sp.ConsoleLog('traveling left: ' + distanceTravelled);

// X axis value started out at
var startX = action.GesturePoints[0].X;

// M.Wheel-scroll-to, horizontally, by n pixels
sp.MouseWheel(new Point(parseInt(startX + distanceTravelled), action.GesturePoints[0].Y), true, parseInt(horizScrollDist));