Adjust horizontal scrolling speed on a mouse or trackpad independent of the vertical speed
You can make the horizontal scroll speed faster and independent by overriding the native ⇧+scroll function with SteerMouse's feature to define a custom relationship between inputs, scroll speed, and direction. You can even assign a scroll speed acceleration value if you want to combine slower and faster scroll speeds for enhanced precision.

Here's how to set it up:


In the SteerMouse preference pane, select the "Mouse" tab.
Switch the "Horizontal scrolling" option from "Tilt" to "Roll" (Fig. 1). This should be enough to let SteerMouse take over the handling of horizontal scrolling, which is what is invoked when you use the native ⇧+scroll function, so if you don't wish to make further scroll speed adjustment, you can stop here.
Select the "Scroll" tab (Fig. 2).
Click the "Roll Horizontally" button.
Make any further acceleration and sensitivity adjustments. You can also invert the horizontal scroll direction (Fig. 3).