Thanks for the topic.
We don’t have the option to show secondary menu in the fixed header, and this requests additional customization in js, php files and css, which is beyond our basic support scope. We can give only tips.
To include JS you need to create etheme-child.js file in your child theme, then add this code –
Also, use this code in function.php file of your child theme https://prnt.sc/gfb65z: wp_enqueue_script('child-theme', get_stylesheet_directory_uri().'/etheme-child.js',array('etheme'),false,true);
add this code in Theme Options > Styling > Custom css: