My girlfriend thought horizontal scrolling on Mac was terrible on some scenarios, Excel, AutoCAD, etc.
El Capitan doesn’t support modify Trackpad and mouse setting.
You may find some keys in
user defaults like these:
Maybe other OSX works fine, but on El Capitan, it doesn’t work as their name!
I modified a utility for reversing vertical/horizontal scrolling to disable horizontal scrolling.
This the diff: https://github.com/dawncold/Scroll-Reverser/commit/194dcdf618b32283413fc8bde825bb279d92fb2f, core code is very small.
Now my girlfriend is happy.