The lovely @imsnif et al. have just released a new version of Zellij (a terminal workspace with split panes and much more).
The latest version brings stacked panes, auto and swap layouts, and floating panes in layouts.
https://zellij.dev/news/stacked-panes-swap-layouts/
(My favourite Zellij feature apart from the panes? You can open the output of the last command run in your favourite editor so you can copy/paste, etc., without using your mouse… if that’s your sort of thing.)