What about a defamation lawsuit? Surely Twitter has repeatedly accused Trump of being a liar. Twitter has done so by publicly stating that Trump has violated its policies on spreading disinformation. So why not sue on the basis that many of these instances involved provably true statements by Trump; thus the claim that they were disinformation has defamed him. Being a public figure means he would probably not win such a case but perhaps he could get lucky with a judge and survive to the discovery stage.
“So why not sue on the basis that many of these instances involved provably true statements by Trump; thus the claim that they were disinformation has defamed him.”
That’s not enough grounds for a suit even, since he is a public figure. He would have to show demonstrable harm as well, and possibly malicious intent too.
A good example of that is the Johnny Depp case, in which he is likely to win because he can demonstrate that he lost a multi-million dollar film contract directly because of the defamation. Trump might be able to make a case that they hurt his reelection chances, but the courts are going to want to see monetary harm, which I don’t think that would satisfy.