Or perhaps, more generally useful would be the diagram 'extract' mechanism that placed the resulting cases into a (e.g.) CSV ["comma separated values"] or other simple-formatted file, which could then be incorporated into many other applications, e.g. Excel.
So the steps would be: parse diagrams, extract relevant content, store in correct format, and you would select the "CSV" option rather than the TestDirector option.
Conversely, you would need to have an idea how the diagram information was used, to ensure that the correct fields were filled in, in the diagram elements.
In general, if someone is [heroically!] creating an AddIn for general use, they would benefit the maximum number of people if they provided a "wiretap" near the end to allow CSV-type data to be exported as well as more proprietary formats.
The resulting output could then be mangled as required by e.g. VBA or Perl, or imported directly.
My £0-0-2 !