This reference guide is about the Application Test Suite (ATS).
ATS is a separate tool which is used to test Mendix applications. It is not part of the desktop modeler. Therefore you can not use this action from the modeler.
PS: From the documentation
The Mendix Application Test Suite (ATS) is a suite of tools for embedding (automated) testing in your application life cycle. - https://docs.mendix.com/ats/general/introduction
Oh ! Okay, I did not get that. which means there is no Mendix system function to retrieve basics elements such as a Page title or so.
Bad luck for us.
Thank you Andrej