Is it permissible to add the word (and gratitude) to "Our Lord, to You be the praise" after rising from bowing in prayer?

Adding the word "wal-shukr" (and thanks) to "Rabbana wa lakal-hamd" (Our Lord, to You be all praise) is not permissible because it was not reported from the Prophet, peace and blessings be upon him, and acts of worship are tawqifiyyah (strictly prescribed and not subject to personal discretion or innovation).