Greetings out there,
You can find the recording of today's session here: https://www.dynamicweb.com/videos/webinars/exchanging-custom-data-between-dynamicweb-and-business-central
In the end I promised an explanation why the last example didn't work, but I'm sorry I have to disappoint you. My whole environment seemed corrupt after the presentation, so I gave up looking for the answer :-)
I made another promise, though, to post the last example here of how you can extend the integration with information that Dynamicweb contains but doesn't send, and attached you'll find OrderAfterGenerateXmlSubscriber.zip which contains a notification subscriber that adds the external id of an impersonation user to the order XML, and in DynamicwebOrdersSubscriber.zip, also attached, you'll find the codeunit that adds this information to the Sales Person Code of the order (line 52-63).
You'll find more information about extending the integration here: https://doc.dynamicweb.com/documentation-9/integration/integration-framework-2/extensibility/extending-the-microsoft-dynamics-365-business-central-plugin-unit
I've also attached the pptx from the webinar.
Feel free to post questions or comments here.