Current behaviour on Mac app using the keyboard shortcut is to go from:
- on zoom in: 100% to 200% to 400% to 800%
- on zoom out: 100% to 50% to 25% to 13% to 6%
It’s clearly a hard coded zoom value to multiply by 2 or divide by 2. The factor of 2 works great if you need to quickly zoom in or out, but falls short in providing users with more control in many situations. It becomes a real pain to use when a more gradual zoom in/out is needed, especially in the absense of a trackpad or a mouse wheel (this affects mac and pc) .
Some use cases:
- during remote screen share (google meet, zoom, etc) what looks fine at 100% on a 32in monitor to the designer is too small on the screen share to the rest of the stakeholders and it requires a 130% zoom for proper viewing.
- There’s a clear difference in overall size when comparing ui in the browser and Figma (widths, text, and all measurements are the same on both: browser and Figma) and zooming out in Figma to 87% is more accurate to what the ui will look like so the designer can confidently pick appropriate sizes.
- In general, depending on monitor size, a designer might need to be in between zoom levels to fit things so they can work better.
Proposal: implement a zoom setting where the user can specify what the zoom value should be. Some common ways people expect zoom to work: A) similar to the browser or other design apps, where it goes 100%, 110%, 125%, 150%, 200%; 
or by choosing from a list (5%, 10%, 25%, 50%, 100%, 200%); C) or even let users save specific zoom levels; D) or allow the current default behaviour of zoom in/out by 2 and have a shortcut, like Opt+Cmd+(±) to zoom by a smaller user defined factor (similar to how a nudge works).
I imagine Figma designers use Figma to design Figma, surely they have the same pains described here.