WC Lancaster filter to show block type if you have WP_DEBUG turned on.

wplancpa-2019-show-block-type.php

<?php
add_filter( 'render_block', 'wplancpa_2019_show_block_type', 10, 2 );

function wplancpa_2019_show_block_type( $block_content, $block ) {
	if ( true === WP_DEBUG ) {
		$block_content = "<h5 style=\"color:salmon\">{$block['blockName']}</h5><div class='wp-block' data-blockType='{$block['blockName']}'>{$block_content}</div>";
	}
	return $block_content;
}