If you are capturing the lead’s full name in one custom field and wanted to display ONLY the first name on the next node, add the below script on the node level.

  var  fullname  = '{full_name}';
  var [fname,lname] =  fullname.split(" ");

Please note:
The example script above ‘{full_name}’ is where you are saving the leads full name. You need to replace this with the field you are using if your field is not ‘{full_name}’.