When I want to insert an image into email or a deep dream program I use, Finder opens with the tiniest size thumbnails and I have found no way to increase the size. I keep hoping upgrades will fix this, and now I have Big Sur and it still is the same: thumbnails are tiny. The usual size option doesn't seem to exist (as it does when I open Finder). I'm a little embarrassed to mention this because I wonder if there is an easy fix that I've managed to miss.