"Used In" Column for Synced Patterns

add_filter( 'manage_wp_block_posts_columns', function ( $columns ) {
    $columns['wpide_used_in'] = 'Used in';
    return $columns;
} );

add_action( 'manage_wp_block_posts_custom_column', function ( $column, $pattern_id ) {
    global $wpdb;

    if ( 'wpide_used_in' !== $column ) {
        return;
    }

    $counts = get_transient( 'wpide_synced_pattern_counts' );
    if ( false === $counts ) {
        $counts = array();
        $rows   = $wpdb->get_col(
            "SELECT post_content FROM {$wpdb->posts} WHERE post_status IN ('publish','draft','private','future')
            AND post_type NOT IN ('revision','wp_block') AND post_content LIKE '%<!-- wp:block %'"
        );
        foreach ( $rows as $content ) {
            if ( preg_match_all( '/<!--\s+wp:block\s+\{[^}]*"ref":(\d+)/', $content, $matches ) ) {
                foreach ( array_unique( $matches[1] ) as $ref ) {
                    $counts[ (int) $ref ] = ( $counts[ (int) $ref ] ?? 0 ) + 1;
                }
            }
        }
        set_transient( 'wpide_synced_pattern_counts', $counts, HOUR_IN_SECONDS );
    }

    $count = (int) ( $counts[ (int) $pattern_id ] ?? 0 );
    echo $count ? esc_html( sprintf( _n( '%d item', '%d items', $count ), $count ) ) : '<span style="color:#787c82">not used</span>';
}, 10, 2 );

add_action( 'save_post', function ( $post_id, $post ) {
    if ( 'revision' !== $post->post_type ) {
        delete_transient( 'wpide_synced_pattern_counts' );
    }
}, 10, 2 );