I also like having a script per project that will get auto loaded when you cd in. An example from a current project:

  #my vimrc knows what to do with this
  export VIM_TAGFILES="$PWD/build/tags,$HOME/.local/var/tags/system,$HOME/.local/var/tags/glib-2.0"
  export CFLAGS=' -g -O0 '

  function autobuild {
    (mkdir -p build
      cd build
      while true; do
        make
        make deploy
        inotifywait -qr -e close_write,delete ../cgi ../test ../Makefile.am ../migrate.sql;
    done)
  }

  function watch {
    tail -f build/app.log build/deploy/app.log
  }

Over time they'll end up with a bunch of other random things. I've tried abstracting a lot of these to their own scripts but every project proves just different enough to make that more complicated. And most of them are personalized enough that they don't go into the project itself.

Another "super power" for shell scripts is writing completion scripts (https://iridakos.com/programming/2018/03/01/bash-programmabl...). I've had some insanely useful one's do things like look up database values to mimic a large complicated third party product, going through it's UI inputting repetitive info, copying files around, etc was reduced to fake-tool<tab><tab><tab><tab>.