In SII Setup there is a parameter named "Include ImporteTotal" to include that optional node in the generated XML but it will only work on certain ocasions.

I would need to include said node when the option was activated or have an event that allows me customize this behavior.

For more detailts on the matter I opened this post:

https://community.dynamics.com/forums/thread/details/?threadid=d706c98a-4469-ef11-bfe2-6045bdda2af8

Thanks in advance.