Integrate Intercom https://intercom.com into Shopify via manual code. Supports both visitors and logged in users

intercom_with_shopify.js

<script>
  // Add this to your theme layout code after the footer
  var APP_ID = "YOUR_APP_ID";
  
{% if customer %}
  // https://help.shopify.com/en/themes/liquid/objects/customer
  window.intercomSettings = {
    app_id: APP_ID,
    name: "{{customer.name}}",
    email: "{{customer.email}}",
    user_id: "{{customer.id}}"
  };
{% else %}
  window.intercomSettings = {
    app_id: APP_ID
  };
{% endif %}
  
</script>
<script>(function(){var w=window;var ic=w.Intercom;if(typeof ic==="function"){ic('reattach_activator');ic('update',intercomSettings);}else{var d=document;var i=function(){i.c(arguments)};i.q=[];i.c=function(args){i.q.push(args)};w.Intercom=i;function l(){var s=d.createElement('script');s.type='text/javascript';s.async=true;s.src='https://widget.intercom.io/widget/' + APP_ID;var x=d.getElementsByTagName('script')[0];x.parentNode.insertBefore(s,x);}if(w.attachEvent){w.attachEvent('onload',l);}else{w.addEventListener('load',l,false);}}})()</script>

Themes > Actions > Edit code > Choose the layout e.g. theme.liquid > Add before the </body> tag