workflow dynamic participant custom email template

Hi, 

Please have a look at this KB article:-

Link:- https://helpx.adobe.com/experience-manager/kb/ParticipantEmailNotification.html

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Question

How can I configure e-mail notifications for a participant step in a workflow?

Answer

Configure Mail Service (com.day.cq.mailer.DefaultMailService). The preferred way to store configurations for OSGi services in CQ is as nodes of type sling:OsgiConfig in JCR repository (see this article). But you can also configure the Mail Service in the Felix Console. The SMTP host, port, user and password are required, as well as "From" address. 
Make sure CQ Workflow EMail Notification Service (com.day.cq.workflow.impl.email.EMailNotificationService) is configured. 
Set Email notification property of the Participant Step to true. 
The e-mail template can be configured under /etc/workflow/notification/email/default. The default template is en.txt. But other languages can be supported by creating <language>.txt file under the same path.

Some reference link which can indirectly help you:-

Link:- https://forums.adobe.com/thread/1107034

// Send Email Using CQ API and custom template

Link:- https://helpx.adobe.com/experience-manager/using/creating-custom-aem-workflow-steps.html

//Creating custom AEM workflow steps that send email messages

~kautuk

You will have to modify the workflow and use a custom step to reference the content you want to use.