I created one custom dialog with an email template field and email subject and message. when I select email template then the subject and message will automatically fetch.
I add a message with jinja format in email template but when I select the email template in my custom dialog then message field not replaced with original field value.
Email Template is not intended to be used in the email dialog (CommunicationComposer JS class), it’s intended for server-sent emails only. I have customized this before for customers and it’s not trivial. To ensure backward compatibility and minimize conflicts, this should probably be added as a feature that uses a new/different doctype instead of Email Template.