Answered by Shaykh Faraz Rabbani
Question: Assalam ‘aleykum
Do we have to perform the forgetfulness prostrations if the supplication for the qunut of witr prayer is omitted?
Answer: Walaikum assalam,
I pray this finds you in the best of health and spirits.
In the Hanafi school, the witr prayer is a necessaary (wajib) prayer, and reciting a supplication (qunut) in it (in the third rakat, after recitation, before bowing) is also necessary (wajib). [Shurunbulali, Maraqi al-Falah; Abidin, al-Hadiyya al-`Ala’iyya]
While the specific, transmitted dua of qunut is recommended, any supplication fulfills this necessary action. [ibid.]
If one fails to recite any supplication for the qunut of witr prayer, then one ommitted a necessary (wajib) action—and forgetfulness prostrations (sujud al-sahw) is due if left forgetfully. [related]
I would recommend taking a course on the fiqh of worship here at SeekersHub, or with a reliable local teacher, for clarity and confidence in your worship of Allah Most High.
Please see: Forgetting to Recite the Qunut in Witr Prayer
Please consider taking this (free) course: Absolute Essentials of Islam: Basic Hanafi Jurisprudence (STEP)
And Allah is the giver of success and facilitation.