There are several I can think of, whose names I draw a blank on.
The Dagger of the Mind actress you mention seemed to make a career out of being an extra. For one thing, in one episode of The Bob Newhart Show where there's a bigger encounter group than usual, she plays a member of it without any lines.
There's also the large man with the kinky hair that Columbo kids about his weight in Identity Crisis. He has a non-speaking role in The Most Crucial Game, and maybe other episodes.
And the actor in The Most Dangerous Match, who plays the reporter who wishes Clayton good luck. He's in a few other ones, like (I think) Double exposure.
Very interesting, John -- thanks for posting! I'm glad you mastered the technique of uploading images to the Forum.
Honestly I thought what you had was probably some instances of "character" actors who made return appearances in small roles, but these are truly bit-players, walk-ons, or extras. It took a great eye for you to spot them making repeat appearances!
Thanks, Ted! And it was thanks to you! Here's one more of our friend, which I just spotted last night while watching "Any Port in a Storm". It appears to be him in the front row at the auction next to the woman in the white fur coat.
There might be some kind of "untold story" there, like he was one of the assistant lighting or sound guys who sometimes was called to get on-camera for a group scene. Kind if like, it was a surprisingly long time, as far as I know, before Mike Lally became a thing that people noticed -- even Mark Dawidziak regrets that he missed it.