Snippet: Add New “Blocks” to the Blog Entry Layout

/**
 * Example function for adding new "blocks" to the blog entry layout manager.
 *
 * After adding your new blocks simply create a new file with the name "blog-entry-YOUR_KEY.php"
 * and place this file at partials/blog/ in your child theme. Make sure to replace "YOUR_KEY" with
 * the key given in the array.
 *
 * IMPORTANT: This module will be disabled by default, so you will have to go to the Customizer to enable it.
 *
 * Default blocks: The default blocks included are featured_media, title, meta, excerpt_content, readmore
 * If you want to show/hide blocks conditionally without affecting the Customizer settings you should use the 'totaltheme/blog/entry_blocks' hook instead which also allows you to display a custom output for your "block" without
 * creating a new template file!
 *
 */
add_filter( 'totaltheme/blog/entry_blocks/choices', function( $blocks ) {
    $blocks['advertisement'] = __( 'My Advertisement', 'textdomain' );
    return $blocks;
} );