That's interesting info, Scootermac. "Gingerly searches out his old usb average logitech mouse, plugs in and scrolls wheel with shift, ctrl, alt, apple-thingy, and all comibs, with no left/right scrolling happening. the sound of a balloon deflating ensues."
Bah. Worth a try. My current mouse is the Logitech M705. Looking in the Control Center (again) I discovered that I could use the wheel tilt option to assign to horizontal scroll, which does actually work. Not as "free wheeling" nor precise as scrolling the wheel, but it does get me left/right movement in Studio one V3(.2).
Hope this helps with your MX master, too.