Hi Gavin,
seeing now, what you have at hand and what you need to achieve, there's a bit more help I can offer
First off, it seems, that you already have a structured document to start with. You can easily recognize this, if you place the cursor in a text line within the document and see the structure view populated with elements.
When this is the case, there's an EDD underlying in your FM binary document file, that you can use and modify. I suspect you already did that, as you already inserted the new elements to it.
Now, having done that, all you need is to re-import the modified EDD back into your document. Russ already stated, that the EDD is ALWAYS tied to the binary FM file, once it has been imported to it.
The external EDD does also have its place in this. Think of it as the "master copy" of your structure (very much like a template). If you are doing changes to the structure, always do that in the external EDD and then propagate it to the binary FM document files when needed.
Now, on a side note, there's also the possibility to have some different workflow.
As your customer is working with XML files only, you could also re-organize your own workflow to be XML based.
FM from version 11 on supports this. In that case FM would only be a wysiwyg editor for XML, and the EDD would become self-propagating (as it creates only a temporary FM binary file, that is scrapped when the wysiwyg view is closed).
But this is quite some different beast to tame. You could evaluate this as a long term goal (once you got a better understanding what you are doing).
So, back to the business problem you are trying to solve at the moment.
After having modified the EDD, this is your todo list for the next steps:
1. re-import the modified EDD to your document file.
2. create a structured application for your documents (if there's not already one used).
3. create a DTD from the new EDD and modify it, so it supports additional information that is needed (like table properties).
4. modify the read/write rules of the structured application you have created in step 2, according to the EDD/ DTD,
5. see, if your document exports correctly to XML.
6. see, if the so created XML file imports back into FM correctly (this step will also need the "master" EDD).
7. fix the issues that occurred during roundtripping (this will most probably be issues with images, tables and whitespacing) in EDD, DTD and RWR.
8. repeat steps 4-7, until you have a working roundtripping solution.
9. fix the issues with UIDs (those will most certainly arise in the process) by FM scripting or with XSLT (depending on what solution you prefer or fits best to your current workflow).
10. explain to the management the you expect a rise in salary, now that you are an expert on document structure management
11. care about further document processing in XSLT and/ or XSL:FO.
12. explain to the management, that you could have matched the deadline, if they had given you training on all this a year _before_ they wanted to see results.
13. see, if you can streamline the process you've set up (check the possibilities of an "XML only" workflow and see if your authors would support it).
14. add new features to the creation process (such as automatic language dependent quote marks, color encoding and other ease of use stuff) - this is where the process you've set up/ knowledge you gained starts to pay off.
Hope this helps your case and gets you going
-Alex