toggle_proxy.fish

#!/usr/bin/env fish

set -x no_proxy 'localhost,127.0.0.1'

function toggle_proxy
    if not set -q http_proxy
        set -gx http_proxy 'http://127.0.0.1:8118'
        set -gx https_proxy $http_proxy
        echo 'Proxy On'
    else
        set -e http_proxy
        set -e https_proxy
        echo 'proxy Off'
    end
end

Add this line to "~/.config/fish/config.fish":

source toggle_proxy.fish