In Zsh, you can set PATH with path=(~/.local/bin $path). There, it works as shell expansion works.

In fish, you can just do `fish_add_path ~/.local/bin`. Adding a directory to your PATH is so common that there’s a function to do it. And it takes effect immediately in all running instances of the shell.

https://fishshell.com/docs/current/cmds/fish_add_path.html