It would be nice to have the option to resize the bottom scroll bar. It’s really tiny! Even if there were just two other sizes to choose.
It shows up better in light mode, which is a shame, since I prefer dark mode.
I would agree, it’s really tiny, and frustrating to use.
I’ve solved it with my Logitech Mouse’s side-scroll wheel. 
Ooooh! I want one!!! 
it’s also almost invisible with Windows 11. A significant frustration with Dorico 6 compared to previous versions.
Any mouse with a scroll wheel can scroll horizontally by holding Shift. (Windows or Mac.)
Yeah, I tend to forget these when I have dedicated hardware for such. I’ve got one on the top of my mouse that adjusts system volume with a gesture.
Oh duh! 40+ years on a desktop computer and I don’t think I ever knew that! 
I was 69 years old when I discovered this worked. Duh!!