Why is the question – "Can God create a stone that he cannot lift" nonsense?

This is certainly a meaningful question, but it is a different question. The question was originally intended to prove that there is no God or that He is not omnipotent. The questioner is trying to corner the believer and prove to him that his position leads to a contradiction. But your question does not do this. Even if I accept that He can make Himself not omnipotent, there is no contradiction in this and hence it is not a challenge to His existence or omnipotence. Conclusion: This is a different question from the one I was talking about. Of course, one can also argue about it. The question is whether his omnipotence is an essential part of his definition, so that when he makes himself not omnipotent, it will not be him. Just as a person cannot turn himself into a mouse, because when he becomes a mouse, it will not be him. He simply destroyed himself and created a mouse.