Registering Styles - GiantLuigi4/StylesPlusPlus GitHub Wiki
Styles++ uses a reloadable style registry, so you don't actually register a style, you instead register a function which registers your styles
To do this, you just call StyleRegistry$addStyleLoader
with a runnable which calls StyleRegistry$register
once for each of your custom styles
StyleRegistry.addStyleLoader(()->{
StyleRegistry.register(new Identifier("stylesplusplus:wavy"), WavyStyle::new);
});