As of JIRA 8.x, the way the email velocity templates are modified is different from the previous JIRA versions.
Before JIRA 8.x, customers could include an Issue Field by following this article: adding custom-fields to email
As of JIRA 8.x, the method no longer works as the structure of the batched notifications is now different.
A new method exists to add Custom Fields to the Velocity templates, but the method is not suitable for Issue Fields.
The purpose of this feature request is to track customers interest in being able to add Issue Fields to batch notifications and also to document a workaround that customers can implement if adding system field to document is a must in the meantime.