If you want to create message contents that may change during a process pass, you can use placeholders.
Procedure
You can use placeholders in both the Subject and Text attributes. Model placeholders for changing contents as follows:
$nameofplaceholder.
The name of a variable can contain only the following characters: A...Z, a...z, numbers from 0 to 9, hyphens (-) or underscores (_).
Placeholders must have identical names in all languages, for example, $process in English, German, and all other languages.
You have used placeholders to model contents that can change during the process pass.
Example