I guess this board is dead along with the site.

I have never heard of such outtakes. In fact, I've never seen any outtakes from any Columbo episode. I know they have them for sitcoms - Everybody Loves Raymond, Seinfeld - but I know of no such for dramas. Not sure if they'd be funny, given the things I've heard about the conflict between Billy Connolly and Patrick McGoohan.

Do tell, that's news to me, what happened with Billy and Patrick?

There were a couple of interesting stories regarding this episode:

https://columbophile.com/2023/06/04/the-mystery-and-murder-of-murder-with-too-many-notes/

And this, in which (near the end) the story of a drunk Billy Connolly gets publicly shamed by Patrick McGoohan.
https://columbophile.com/2023/04/30/columbo-episode-review-murder-with-too-many-notes/

I may have come across more details of the conflict on the set between these two, but I can't recall exactly where.

There might be some on YouTube, maybe among general Columbo outtakes?