Every key from a bot behavior’s dictionary is automatically available as a placeholder.
As far as template scripting is concerned, placeholders are variables. Anything you can do to a variable, you can do to a placeholder.
I am the placeholder's value
When building a template, you can use the Insert placeholder menu to browse and select placeholders.
To set or change a placeholder, you must use the Set custom placeholder action in a behavior, rather than the set command in a template.
The value of a placeholder can be set with a template referencing other placeholders.