These attributes are only applicable if the Action attribute is CreateVariable. This allows to specifiy either a variable name (attribute VarName) or a prefix for the variable name (attribute VarNamePrefix). In the latter case, the actual variable name will be built from the given prefix and the actual string value during recording.
The attribute IsExternalVar (boolean, Default: false) can be used to suppress the scripting of a declaration for the variable. This is useful if it is known that this variable is already declared in some bdh-file within a SilkEssential.