What is the ruling on someone who recites the supplication: "My Lord, expand for me my breast and make easy for me my affair" during prayer instead of the glorification in prostration or the supplication between the two prostrations, or after the glorification in prostration, and then performs the two prostrations of forgetfulness before the Taslim?

Verbal additions in prayer—such as supplications, remembrances, takbir, and tasmi'—do not invalidate it, even if the worshipper performs them out of their proper place or prostrates for them. Some scholars are of the opinion that prostrating for them is recommended, not obligatory, because it is a rectification for something not obligatory. Therefore, your prayer is valid, and there is nothing upon you, but it would have been better not to prostrate for this oversight.