Here's an example of how to remove Subject field from the embedded widget Ticket Submission form. Add this code right after LiveHelpNow embedded widget code:
    function lhnJsSdkTicketShown(){
      lhnQuery('*[placeholder="Enter subject"]').val('website inquiry').closest('.lhnField').hide();
    }
  
  
    function lhnJsSdkEmbeddedOpened(){
      // This function will be called when the embedded window is opened
      lhnQuery('#lhnWindowCloser').click(function(){lhnJsSdk.closeHOC();lhnQuery('.closechat').hide();});
    }
  
  
    <script type="text/javascript">
    function lhnStatusUpdate(){
      if(lhnJsSdk.isOnline == true){
        //do something when online
      }else{
        //do something when offline
      }
    }
    </script>