My apologies for just now seeing your question. I have forwarded it to the Braille2000 experts on the committee and will send you their response once I have it. Stay tuned!
Here is the response from one of our Braille2000 experts:
Use Ctrl+F, type in the opening TN indicator. Above the search bar, click Extend. Type the closing TN indicator. Click Extend All. This should highlight all TNs in the volume. Finally copy them.