This will add the link to the interface for managing reusable blocks to the WordPress side menu.
Snippet
Add this to your functions.php, or your preferred code snippet manager.
function be_reusable_blocks_admin_menu() {
add_menu_page( 'Reusable Blocks', 'Reusable Blocks', 'edit_posts', 'edit.php?post_type=wp_block', '', 'dashicons-editor-table', 22 );
}
add_action( 'admin_menu', 'be_reusable_blocks_admin_menu' );
