When viewing a Figma design file, you can zoom in/out with CMD and up/down on
a trackpad or magic mouse.
Scroll left or right with one-finger swipe left or right.
Zoom and scroll; along with adding comments and copying CSS, that's most of what I do in Figma.
I'm sure that these commands are useful in many other settings, but I find them especially valuable in a Figma file, which can feel otherwise challenging for me to navigate.