[Lynne]

This is not as easy as you seem to think it will be. You will need to:
- add a new field to the thread table
- add a new field to the post table (optional?)
- modify the save post function to save this new field when a new thread or post are made
- modify the get threads query to get this new post title also
- modify any display templates (or the code) to display this new post title if that language is selected
- modify search to allow for searching of this field (optional)

This isn't some modification anybody is likely to write for you unless they have need of it themselves and want to code it in such a way to share. It's much more involved than just adding some new text area to your new thread page.