this gist is a combination of these two links:
running scripts on macos startup and get-borderless-arc repo
open automator.app
select "new document"
select "application"
select "run shell script"
paste the following
# Download the script and make it executable
curl -O https://raw.githubusercontent.com/ifvictr/get-borderless-arc/master/get-borderless-arc.sh
chmod +x get-borderless-arc.sh
# Run it
./get-borderless-arc.sh
press ctrl + s
name it "get-borderless-arc.app"
press enter
open settings
go to login items
click on +
search for "get-borderless-arc"
select it and press enter
now the script will run on startup
and you will have the option to toggle arc border using cmd + shift + b