I knew it was somewhere but just couldn't remember where that somewhere was.
The setting on Mac is a general Mac setting that's applied to all Mac applications - it's in Mac's System Preferences, not in JMP.
On Windows, there is a limit to the number of recent files that can't be changed. I think that number is north of 200. Are you finding that to be inadequate?
This post just got me thinking and my curiosity got the better of me. I don't have an issue with the default setting s on a Windows system. I just thought it might be interesting to increase the quantity. Thank you for inquiring.