ブロックバリエーションを作成してカスタムフィールドを出力するサンプル

block-bindings-custom-fields-test.php

function book_introduce_block_type_variations( $variations, $block_type ) {
	if ( 'core/heading' === $block_type->name ) {
		$variations[] = array(
			'name' => 'book-title',
			'title' => 'Book Title',
			'attributes' => array(
				 'metadata' => array(
					 'bindings' => array(
						 'content' => array(
							 'source' => 'acf/field',
							 'args' => array(
								 'key' => 'book-title',
							 ),
						 ),
					 ),
				 ),
			),
		);
	} elseif ( 'core/image' === $block_type->name ) {
		$variations[] = array(
			'name' => 'book-thumbnail',
			'title' => 'Book Thumbnail',
			'attributes' => array(
				 'metadata' => array(
					 'bindings' => array(
						 'url' => array(
							 'source' => 'acf/field',
							 'args' => array(
								 'key' => 'book-thumbnail',
							 ),
						 ),
					 ),
				 ),
			),
		);
	} elseif ( 'core/button' === $block_type->name ) {
		$variations[] = array(
			'name' => 'book-amazon-url',
			'title' => 'Book Amazon URL',
			'attributes' => array(
				 'metadata' => array(
					 'bindings' => array(
						 'url' => array(
							 'source' => 'acf/field',
							 'args' => array(
								 'key' => 'book-amazon-url',
							 ),
						 ),
					 ),
				 ),
			),
		);
	}

	return $variations;
}
add_filter( 'get_block_type_variations', 'book_introduce_block_type_variations', 10, 2 );

参照：https://olein-design.com/blog/show-custom-fields-value-by-block-variation