I’ve used Scrivener for a little while, and have created a number of custom formatting presets. However, I can’t see how to restore my list of presets to the default settings. How should I do this?
Using the main Scrivener application menu, select the “Reveal Support Folder in Finder” menu command, and then remove or rename the “Styles.plist” file. You might need to restart the software after doing so.
Superb, thank you! I guess that making a copy of that file will also allow me to maintain multiple formatting presets 
Yup! Good for backups too, and even syncing (so that all Macs use the same central preset file).