A killer feature for me is combining floating windows with "zellij run". It allows you to run a command but also re-run the command by pressing enter.
zellij run --floating -- date
This will open a new floating window with the result of the command (`date` in this case) and pressing enter will run it again. I use it for running tests (make some changes, show floating windows, press enter). Depending on your OS you might already have shell aliases such as zrf (run floating) or zr.
Not really but where do you press these? Say I have the editor full screen. Do I switch to a different tab/split/window? In Zellij I press <meta+f>+<enter>. Pressing <meta+f> again will hide the floating window and I'm right back in the editor. I don't use this all the time, sometimes I have a terminal open in a split, but it can be pretty convenient.
I use iTerm in visor mode, so ctrl-~ (tilde) shows my terminal tabs and changes focus to them. Pushing it again hides them and returns focus to the previous app.
https://zellij.dev/documentation/zellij-run