Is the method of seeking aid (Istighatha) valid by gathering people in an open area, with scholars sitting at the forefront, seeking Allah's forgiveness (Istighfar) and aid (Istighatha) from Him, when there is a tribulation (fitna) affecting the subjects and Muslims?

The action mentioned in the question is an innovated Bid'ah (innovation), as the gathering of people, collective seeking of forgiveness, and collective seeking of aid from Allah the Almighty are not mentioned in the Sharia. The Messenger of Allah (peace be upon him) said: "Whoever introduces into this affair of ours anything that does not belong to it, it will be rejected." Al-Nawawi said: "This hadith is a great principle among the principles of Islam, and it is among the comprehensive words of the Prophet (peace be upon him), for it explicitly rejects all innovations and newly invented matters."

Supplicating to Allah and seeking His aid in times of calamity is legislated. Allah has indeed reproached peoples who did not supplicate to Him in times of adversity, saying: "Then why did they not humble themselves when Our adversity came to them? But their hearts became hardened, and Satan made attractive to them that which they were doing." Some jurists hold the view that prayer is legislated in times of fear, but gathering for that purpose has not been legislated by the Sharia.