Salatul Tasbih in congregation
In the name of Allah, the most Beneficent, the most Merciful.
Answer
It is Makruh to hold congregation for nafl prayers. Therefore, as Salatul Tasbih is a nafl prayer it will be Makruh to perform it in congregation.
However, if a group of people gather (4 including the Imam) and do the Salah in congregation it will be permissible according to the view of Imam Muhammad. (Raddul Muhtar p.500 v.2 & Badaaius Sanaii p.290 v.1)
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham