Is it permissible to continue performing supererogatory congregational prayers after ʻIshāʼ, concluding them with three rakʻahs of Witr prayer audibly with one taslīm, according to the Hanafī school of thought?

Voluntary prayers in congregation are of two types:

First: Those for which regular congregational prayer is Sunnah, such as the eclipse prayer (Salat al-Kusuf), the prayer for rain (Salat al-Istisqa), and the night prayers of Ramadan (Qiyam Ramadan). It is preferable for these to always be performed in congregation.

Second: Those for which regular congregational prayer is not Sunnah, such as the night vigil prayer (Qiyam al-Layl), the regular Sunnah prayers, the forenoon prayer (Salat al-Duha), and the prayer of greeting the mosque (Tahiyat al-Masjid). It is permissible to perform these occasionally in congregation. However, consistently performing them in congregation is not legislated; rather, it is a disliked innovation (bid'ah makruhah) because the Prophet (peace be upon him), the Companions, and the Successors did not habitually gather for them. The Prophet (peace be upon him) mostly prayed the night vigil individually, and he prayed it in congregation on rare occasions. Therefore, it is not permissible to consistently perform the night vigil prayer in congregation, but there is no harm in gathering for it occasionally.