Bambi addon is an addon to psych engine which adds support for lua in basically every state, as well as the ability to create custom states! Theres more features than that, too. Every tween function has been deprecated by a single doTween function, which works exactly like flixel tweens!. Most modified states also have state-specific functions! This addon also adds base game hscript support! They load the same way as lua scripts (ex: a script named script.hx in the scripts folder)
List of things you can do: Freeplay categories, new main menu options/override originals, new options, new gameplay changers, change where base states go on exit, and so much more!