A block style variation instead of a custom class

A “quiet” button, applied by an editor adding a class in the advanced panel, which nobody could discover and half of them misspelled.

register_block_style( 'core/button', array(
    'name'  => 'quiet',
    'label' => __( 'Quiet', 'turkerdev' ),
) );

// and the styles, keyed on the generated class
.wp-block-button.is-style-quiet .wp-block-button__link {
    background: transparent;
    color: var(--wp--preset--color--ink);
}

A registered style appears in the block’s own panel with a preview, which is the difference between a feature and a piece of folklore. The class name is generated, so it cannot be misspelled, and removing the style later shows up as a block whose variation no longer exists rather than as a class that silently does nothing.