Thanks Gadget Fiend for the heads up about X-Mouse Button Control.
Took me a while to get it sorted.
Just a tip for anyone else looking to get their horizontal scroll working as it should…
If you just select “invert mouse wheel” in the scrolling and navigation tab, it will invert it for EVERYTHING in Cubase (assuming you have created a profile for Cubase. This means that scrolling through menus and zooming with CTRL will all be reversed too, which is not good.
To get invert the mouse wheel just for horizontal scrolling, don’t touch the navigation tab.
Instead, go to the “Layer 2” tab and set Mouse wheel up to Wheel down and set Wheel down to wheel up.
Then, click on the “Settings” button and go to the “Modifier keys” tab.
For “Activate Layer 2”, choose “SHIFT”.
Click on “OK” and then “Apply”
That will invert the mouse wheel only when you hold SHIFT in Cubase.