Thanks for pointing out the scripting solution. It seems 40 is the current minimum via the slider, right?
After a quick test on my iMac 24", I’d say:
• 20 is very small but sometimes it could be useful for seeing the whole font. Could be a sensible minimum for the slider. At this size, the overall layout could be more compact, and the indentation (and size) of the category names feels too large.
• 30 feels comfortable for general use.
• I see the point for using a very large size for proofing purposes, though, something like 300-400 maybe.