Hello @QiZhang
As you already mentioned - Comment Field can be generated by JavaScript code using an example given in this community topic -
Pull in all comments for an issue - #9 by DennisT. Once this custom Comment Field is created, you can select the field for import through your account Source Data → Jira Import options → Custom fields. If you only need this field for one specific project, it might be a good idea to create a new account in eazyBI and import the newly created custom field only in that particular account and use this account for your specific project.
Let me know if I missed something and if you have further questions!
Kind regards,
Elita from support@eazybi.com