I know "the user is never wrong" but I think the mental model does not quite match. Your changes are always immediately persisted in the preset so after tweaking it you already end up with your perfect preset.
But most experiments lead to nothing, so in your example, more often than not, I will have messed up my preset with no way to undo
I know you can "right click>duplicate a setting and use that for testing, than when you are satisfied relink the setting and delete the old one" but that's very unintuitive and cumbersome.
I was hoping that changing the default behavior of the "new preset" button would take away at least some of the pain of the workflow above.
But since you brought it up: I also struggle a LOT with the auto-save . The 2.9 version had a superior workflow in that regard (and 3.0 a better UI). It discourages experimentation. It also increases the chances of someone on the team (we share a model with many designers) will accidentally mess up someone's settings.
Rather than auto-save, why not have a save button, and perhaps a warning when you are about to switch to another preset (or close the settings panel) whether you want to save/discard any unsaved settings. You would achieve the same thing as auto-save (not accidentally losing any settings) while giving users an options to experiment/make mistakes without irreversible damage.
I did a small training yesterday on the Enscape settings and polled people on whether they preferred the 3.0 or 2.9 handling of presets. Although the UI of 3.0 was preferred, all 5 people preferred the explicit save of 2.9.
It's also important to note that Enscape doesn't exist in a vacuum. People have gotten used to certain software paradigms because they exist in so many other programs. Many programs that we use has the concept of 'presets', but almost all of them have the option to save/cancel changes to them.