Using shortcode in functions.php

Hi,

I’m trying to a get a lightbox shortcode working with a the below string in my functions.php file:

add_filter( 'woocommerce_attribute_label', 'custom_attribute_label', 10, 3 );
function custom_attribute_label( $label, $name, $product ) {
    $taxonomy = 'pa_'.$name;

    if( $taxonomy == 'pa_size' )
        $label .= '<div class="custom-label">' . __('MY TEXT', 'woocommerce') . '</div>';

    return $label;
}

The idea being that next to the ‘MY TEXT’ it would say ‘MORE INFO’ and if you click on that that lightbox would pop up with a sizing diagram.

I can see on the SU docs, that shortcodes can be used in template files here: https://getshortcodes.com/docs/using-shortcodes-in-template-files/

Would it be something like this (using the example lightbox shortcode from the site?

$content = ‘Click here to open lightbox with an image’;
$my_shortcode = ‘[su_lightbox type=”image” src=”https://placekitten.com/720/480″%5D’ . $content . ‘[/su_lightbox]’;
echo do_shortcode( $my_shortcode );

And if so, but where do I need to add that into the code string to allow the lightbox shortcode to work?

TIA

Nick