append xml twine retard existent xmldocument

i have an xmldocument already exists review file.

i supplement brick xml node document. there good proceed emanate supplement nodes but cluttering formula .createnote .appendchild calls?

i proceed origination twine stringbuilder current xml domain only appending an xmlnode.

ex:
original xmldoc:

<myxml>
   <employee>
   </employee>
</myxml>

and, i supplement demographic (with several children) add-on employee:

<myxml>
   <employee>
      <demographic>
         <age/>
         <dob/>
      </demographic>
   </employee>
</myxml>