Hi, to be honest this question lacks some additional information, but I presume you are repeating
your previous question.
Well the easiest solution that comes to my mind is to use Hidden Text or TC field, before the embedded text, to store your ids.
But everyone can view this information by pressing "Show/Hide" in MS Word so I do not believe this would work for you.
Another solution that you can try is to create a Custom XML Part in your DOCX, unfortunately I do not have a lot of experience in this part of a DOCX, but I hope this will lead you to the required solution.
Also there are lot of information about it, just search "OpenXml SDK Custom Xml".
In short I believe what you are looking for is these two elements in the DOCX specification under the "Custom Markup":
- customXml (Custom XML Element)
- attr (Custom XML Attribute)