By default, several fields do not display in the default Email Template such as the Hidden Field, Invisible Field, Section Heading Field, Private Notes Field, and Custom HTML field.
If you'd like to display any or all of those fields, you can override the default email template by in your Notification Email settings. Select the "Custom Templates" option and add a path to a folder in your template folder where you will place your email.twig
override file. More info on Notifications and Email Template overrides in our docs.
You can copy the default Email Template as a starting point and the line that you'll want to update is {% for field in fields if not field.isPlainInput() %}
which you can see here.
You can remove the if not field.isPlainInput()
condition in that for loop to display all fields in your email. And conditionally hide or handle other fields uniquely in your templates by targeting them by their unique folder name: field.getFieldInputFolder()
.