On the smart app screen the nest app has a play icon
You will get the fastest answer if you ask your question in the author’s thread for the code for that smart app.
The author will be automatically notified of new questions, and other people who are using the code may also be able to help.
That is called an App Touch feature (if my memory serves) and it can send an event to the app that displays that button. What that event does after that is entirely up to the developer, so at this point what NST Manager does is really something perhaps @tonesto7 could explain…