As far as I know, preference files are supposed to be in ~/Library/Preferences/ and use the
reversed-domain-notation for the filename. So I assume for processing, the file should be:

~/Library/Preferences/org.processing.txt
or
~/Library/Preferences/Processing/preferences.txt

If this is wrong or not wished, please feel free to ignore it.

HTH, Andy

it's just a cross-platform thing. we just refer to preferences.txt in tons
of places in the documentation, and there are enough caveats about its
location with regards to each platform without having to change the name
for each platform as well. so we'll just keep it as preferences.txt.