I have thought more about this from something I mentioned recently,
Mr D Van D in Negative Reaction when he says he can't offer Columbo anything because he doesn't drink, at a real life time period when D Van D was publicly well known for talking about his alcoholism.
In A Trace of Murder, when Columbo says three eyes are better than two.
In Uneasy Lies The Crown, Nancy Walker playing herself in the context of being an actress in the Mystery Movie series of which the Columbo films were part of. Also in the episode Columbo talks about Peter Falk's real life good friend Dom deLuise.
I don't know if the following define the Fourth Wall,
Columbo as a toy soldier in the episode Grand Deceptions.
Columbo as a circus ringmaster in Murder Smoke and Shadows.

Are there others?

After watching Uneasy Lies The Crown, many, many times over the years, I realised there is another, the writers to the viewers, whether it was intended I don't know?
When Columbo goes to Wesley's house for the first time and they are talking about the situation, Wesley says that he doesn't know what was going on around the house etc. because he was at the card game, and Columbo says "Very good!!", obviously making it sound like Wesley created a good alibi, and Columbo is complimenting him (but he's going to get him in the end, because he knows he's lying), then he says "The bagel, it's very good".
At that point only the writers and the viewers know what Wesley did, Columbo knows nothing, so for that dialog to be relevant it would be the writers to the viewers.

I should have realised another one in A Trace of Murder, near the end when Columbo bites the end off the cigar and spits it out by Barney's feet, but he shields the view of him doing it from the viewers.