I'm not sure how those comments address the need for a built-in table element with the said features. Can you explain, or link to demo that shows what you are trying to say?
https://www.mozilla.org/en-US/firefox/features/picture-in-pi...
https://old.reddit.com/r/PleX/comments/mr1k8m/just_discovere...
https://news.ycombinator.com/item?id=43121881
https://www.mozilla.org/en-US/firefox/features/picture-in-pi...
https://old.reddit.com/r/PleX/comments/mr1k8m/just_discovere...
https://news.ycombinator.com/item?id=43121881