Permissibility of performing Sujud-ul-Sahw in case of additional actions before or after Taslim

A: Sujud-ul-Sahw for adding extra part to the Salah may be performed before Taslim or after it. Accordingly, what the Imam did in the question was right and the Salah is valid for both the Imam and the Ma'mums (those being led by an Imam in Prayer).