Is it permissible to say in supplication, "O Lord... when is Your victory?" upon witnessing the state of Muslims?

There is no harm in saying that if it is for the purpose of seeking victory and wishing for it, not out of doubt or suspicion. Al-Alusi said in "Ruh al-Ma'ani" when interpreting the verse: (Or do you think that you will enter Paradise while such [trial] has not yet come to you as came to those who passed on before you? They were touched by poverty and hardship and were shaken until [even their] messenger and those who believed with him said, "When is the help of Allah?" Unquestionably, the help of Allah is near.) that the Messenger and the believers say it seeking and wishing for help, and due to the prolonged duration of hardship. Ibn Kathir said that they were seeking victory over their enemies and praying for the nearness of relief.