Creating a Config Class

@Config(name = "modid")
class ModConfig implements ConfigData {
    boolean toggleA = true;
    boolean toggleB = false;
    
    @ConfigEntry.Gui.CollapsibleObject
    InnerStuff stuff = new InnerStuff();
    
    @ConfigEntry.Gui.Excluded
    InnerStuff invisibleStuff = new InnerStuff();
    
    static class InnerStuff {
        int a = 0;
        int b = 1;
    }
}

The Gui generator works with boolean, int, long, double, float, String, and enum types by default.

You can also use it with nested objects by adding the @CollapsibleObject annotation to the object's field. You can register your own providers if those default ones aren't sufficient for you.