He has been told often enough that an actual lawsuit would require discovery and a deposition.

Michael Wolff has been on the Trump beat since long before Trump was president. He was around, if memory serves, for the NYC party years.

If anybody has evidence, besides David Pecker or Putin, Michael Wolff would. He also might have details on a rumored mental health / drug hospitalization of Trump in the Studio 54 era.

to hear evidence as to how it has affected her reputation.

It is quite literally insane for anyone to claim what Hunter Biden said was defamatory. He didn't make it up. When he said it, he said exactly where he was getting it (from a public interview with Michael Wolff) and the same fact about their meeting has been repeated in literally hundreds of news articles from major news sources over the years.

Defamation: the act of harming another person's reputation by making false statements. It encompasses both libel (written defamation) and slander (spoken defamation). To be considered defamation, the statements must be false, published to a third party, and cause harm to the individual's reputation.

3 things must be true

1) the statements must be false - actually, the statements need to be shown that they were known to be false when made. Public figures must prove "actual malice," meaning the statement was made with knowledge of its falsity or with reckless disregard for the truth. Hunter Biden had every reason to believe the statement was true (and of course it has yet to be proven that it isn't true). There was no malice or reckless disregard for the truth. He attributed the statement to respected journalist/author Michael Wolff who has had personally interviewed both Jeffrey Epstein & Donald Trump many times and has hundreds of hours of recordings of his Epstein interviews. Wolff almost certainly has a recording of Epstein making that statement.
2) published to a third party
3) cause harm to the individual's reputation - I'd love to see Melania's attempt to show that a statement by Hunter Biden harmed her reputation. Particularly since he was repeating a statement made by author Michael Wolff (and attributing it to him) and repeated by hundreds of journalists over the years - and nobody was ever sued for defamation for making that statement. So why does she think when Hunter Biden said it, it was defamation but when everybody else said it, it was not?

that is until the official kristofascist gop Cancel Culture censor freaks got into the act.