Is it permissible to perform Salat al-Hajah and the tasbihats in congregation? May Allah reward you.

Voluntary prayers are permissible both individually and in congregation, because the Prophet, peace and blessings be upon him, did both. Most of his voluntary prayers were performed individually, and occasionally he prayed with some of his Companions in congregation. Performing voluntary prayers in congregation is not disliked, but it should not be made a regular sunnah, like someone who is appointed as a resident imam for the mosque to lead people in voluntary prayers in congregation, just as he leads them in the five obligatory prayers.