How to append a new attribute in a xml using scala and sbt?

Question

I have a use-case where I need to append an attribute to a complex xml file, I have referred " Add or append new element to XML file in Scala instead of replacing it " which works to a extent but not on the inner childs of the xml.

XML I am working with :

<persons>
    <person id="1">
        <firstname>James</firstname>
        <lastname>Smith</lastname>
        <middlename></middlename>
        <dob_year>1980</dob_year>
        <dob_month>1</dob_month>
        <gender>M</gender>
        <salary currency="Euro">10000</salary>
        <addresses>
            <address>
                <street>123 ABC street</street>
                <city>NewJersy</city
                <state>NJ</state>
            </address>
            <address>
                <street>456 apple street</street>
                <city>newark</city>
                <state>DE</state>
            </address>    
        </addresses>    
    </person>
    <person id="2">
        <firstname>Michael</firstname>
        <lastname></lastname>
        <middlename>Rose</middlename>
        <dob_year>1990</dob_year>
        <dob_month>6</dob_month>
        <gender>M</gender>
        <salary currency="Dollor">10000</salary>
        <addresses>
            <address>
                <street>4512 main st</street>
                <city>new york</city>
                <state>NY</state>    
            </address>
            <address>
                <street>4367 orange st</street>
                <city>sandiago</city>
                <state>CA</state>    
            </address>    
        </addresses>            
    </person>
</persons>

I would like to add the value in that too after state, is it possible ?

Thanks in advance.