Gutenberg: Custom Block Category

block.js

registerBlockType( 'loomo/yoshi-cookies', {
	category: 'mario-blocks', // Block category

init.php

<?php

function my_mario_block_category( $categories, $post ) {
	return array_merge(
		$categories,
		array(
			array(
				'slug' => 'mario-blocks',
				'title' => __( 'Mario Blocks', 'mario-blocks' ),
			),
		)
	);
}
add_filter( 'block_categories', 'my_mario_block_category', 10, 2);