A microflow would do the trick. In the microflow, you'll create the logic to split up the information into the appropriate entities for the XML export.
Hope that helps,
Per your request, here is an example of posting contact info (name, email address, phone) from a Mendix contact to Hubspot, a marketing automation too:
Here is the data model:
Here is the microflow that creates the Mendix objects and posts to Hubspot:
And here is the nested microflow (highlighted in yellow above):
Hope that helps.
Brett, for XML mappings in 5.13.1, you often will use a simple microflow to return the same object you already have, just one level down the XML tree. So, you could set up your mapping like this:
with settings like this:
and a microflow like this: