Is it permissible to combine two or more intentions in a single supererogatory prayer, such as Qiyam al-Layl, Witr, and Salat al-Hajah?

There is no objection to combining the intention of Tahiyat al-Masjid (greeting the mosque prayer) or Istikhara (prayer for guidance) with another prayer, such as a fard (obligatory) prayer or general supererogatory (nafl) prayers. He will receive the reward for Tahiyat al-Masjid or Istikhara if he intends both together. As for other supererogatory prayers, they do not suffice for one another. And Witr prayer cannot be performed with two rak'ahs because it is an even number.