You need to do some customization and may need to alter posts table. What I am describing here is just for an idea and a logic but there could be a better way to do.
Create a column in qa_posts "answer_title" or if you want to create new table do that with FOREIGN KEY to answer ID with CASCADE
Add a text input field to the new answer form as well as edit answer form using layer.
On answer create or edit event store/update the "answer_title" value to the newly created colum or table (a_post and a_edit)
Fetch the value from the table using custom query or modifying the list array variable (I haven't tested it yet but I am sure you can at least get by custom query if not modifying the list array variable)
All is done...