Hiding Out of Stock Attributes

[SteveG]

So Pagebuilder does this; it uses the opacity to reduce the visibility. I want to make them even less visible by changing the opacity to 0.1 or 0.2. I can't work out how to do it, as it seems it is locked, reading about mmx-customizations items need to be in the mmx base to be available, and the mmx-form-radio isn't. Is there another way?

.mmx-form-radio {
& .mmx-form-radio__input, & .mmx-form-radio-input {
&:disabled + .mmx-form-radio__caption, &:disabled + .mmx-form-radio-caption {

1. opacity: 0.5;
2. cursor: not-allowed;

}
}
}