How could we add other social media icons on the header? For example WeChat or Email icon. Thank you so much!

Hugo

The easiest way would be to override your header.php template in your child theme.
Then after this section you can hardcode your own icon links:

foreach($header_icons as $header_icon){
	echo "<a target='_blank' 
			href='". ( $header_icon['icons_service']!='rss' ? $header_icon['icons_url'] : get_bloginfo('rss2_url') )."' 
			class='header_soc_icon'
			".(!$header_contacts_position_is_left? " style='float: left;'": '')."
			title='". esc_attr($header_icon['title']) ."'>
			<span class='icon ". esc_attr($header_icon['icons_service']) ."'></span></a>";			
}
}

like so:

echo "<a target='_blank' href='LINK' class='header_soc_icon' ".(!$header_contacts_position_is_left? " style='float: left;'": '')." title='TITLE'> <span class='icon CLASS'></span></a>";

You would replace the LINK, TITLE, CLASS in there with your custom strings and you are good to go!