HTML in Header Label?

Hi,

I would like to have the header label in 2 lines, i.e. a line break.
How can I add HTML to the header label?

Example:

Table of Contents
That's what you'll find in this article

Any idea please, for example a snippet to my functions.php?
For HTML in widget titles I use for example this:

function html_widget_title( $title ) {
    //HTML tag opening/closing brackets
    $title = str_replace( '[', '<', $title );
    $title = str_replace( '[/', '</', $title );
 
    //<strong></strong>
    $title = str_replace( 's]', 'strong>', $title );
    //<em></em>
    $title = str_replace( 'e]', 'em>', $title );
	//linebreak
  	$title = str_replace( 'br]', 'br />', $title );
    return $title;
}
add_filter( 'widget_title', 'html_widget_title' );

Can I add anywhere something similar to make a <br /> in the header label of this plugin please?

Thanks.