From - nextgenhealthcare/connect#5193 (comment)
PS C:\Program Files\Mirth Connect\server-lib> java -jar .\rhino-1.7.13.jar Rhino 1.7.13 2020 09 02
js> x = <A/>
js> x += <B/>
<A/>
<B/>
js> x = <A/>
js> x.appendChild(<B/>)
<A>
<B/>
</A>
From - nextgenhealthcare/connect#5193 (comment)
PS C:\Program Files\Mirth Connect\server-lib> java -jar .\rhino-1.7.13.jar Rhino 1.7.13 2020 09 02
js> x = <A/>
js> x += <B/>
<A/>
<B/>
js> x = <A/>
js> x.appendChild(<B/>)
<A>
<B/>
</A>