How to add custom fields to the custom email templates?
In order to use custom fields in your own email templates, you should start adding/editing the template using the instruction here.
You can put custom fields to the template in 2 ways:
1. Using name
$issue.getCustomFieldValue($customFieldManager.getCustomFieldObjectByName('Name Of Custom Field')).toString()
where ‘Name Of Custom Field’ should be replaced with your custom field’s name
2. Using ID:
$issue.getCustomFieldValue($customFieldManager.getCustomFieldObject('customfield_ID)).toString()
where customfield_ID should be replaced with your custom field’s ID (E.g. ('customfield_10800')