You could check the code of the Extra Question Field plugin .
The plugin manages extra fields for questions (ask form and edit form), but you could find something useful to implement the same behaviour for the answers.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.