Wanting to undo tmux breakout pane I've searched for answer, found it, but as it seemingly addressed a similar problem and didn't work for me I asked my own question. Turns out, I should've read deeper, or change perspectives and read, as when few folks kindly pointed out my question was a dupe, I re-read the question they pointed to and found one remark, that in the end was crucial to the answer.
So, my question has the answer there. It is a dupe. I'm now wondering, if I'd found it without being pointed that my question is a duplicate. So, for obvious bias, I'm turning here for an answer.
My tmux question: Bring a broken out pane back to window in tmux
I'm pondering: DELETE, leave for two weeks and see if anybody has that problem, then leave or delete, leave. Advice from other members is welcome.