I checked all the Yammer developer documentation, I cannot find anyway to add a new action inside Yammer, integrated with another Yammer APP similar to the recognize button action in Yammer for Recognize APP (check image below).
Please let me know from where to start if you have any idea.
According to the Recognize site, the addition of actions to the Yammer publisher is done through Recognize's browser extension and not through any Yammer platform API.