You can customize any of the pre-defined rule presets and save the results as a new rule preset. There is no practical limit for the number of user-defined presets so you can create a whole library of your own rules.
Tip: You can save the rules of the currently on-going game (provided that the rules are customized) by opening the Preferences dialog box and choosing Save As New Preset from the pop-up menu. This is handy if you have loaded a game which uses customized rules that you wish to save for future use (this allows you to exchange rules with other players simply by sending a saved game file). Notice that Four Winds reverts to default rules (the ones that were active before you loaded the saved game) as soon as you close the saved game, so if you want to continue with the same settings (and they differ from those that were active before), you'll first have to activate the rule preset to which you saved the settings.
Related topics:
Overview
Guidelines for customizing rule presets
Customizing a rule preset
Modifying a user-defined preset
Renaming a user-defined preset
Deleting a user-defined preset