Hi Don-6186,
It sounds like you're not working at the file format level but attempting to use VSTO api's to embed an OLE object in a Word document. And the question about whether it can be done in a margin is likely better answered by the Word end user support team. If this is correct, then I would suggest adding the office-vsto-com-dev and office-word-itpro tags as well. If you are working at the file format level, manipulating Office Open XML (ISO 29500), then you could perform the action in the Word UI and inspect the underlying format changes. If it's not clear what some piece of XML means or how it's used, you can ask here with the openspecs-office tag. Make sure you are specific about which part of ISO 29500 or our Open Specifications (1fd4a662-8623-49c0-82f0-18fa91b413b8) you need explained.
Best regards,
Tom Jebo
Sr Escalation Engineer
Microsoft Open Specifications