I often write multi-line commands in my zsh shell, like while-loops. The nice thing is that I can readily put them in a script if needed.
I guess that somewhat breaks with fish: either you use bash -c '...' from the start, or you adopt the fish syntax, which means you need to convert again when you switch to a (bash) script.
I guess my workflow for this is more fragmented. Either I’m prototyping a script (and edit and test it directly) or just need throwaway loop (in which case fish is nicer).
I also don’t trust myself to not screw up anything more complex than running a command on Bash, without the guard rails of something like shellcheck!