add it to the target value at the end of the shortcut, it'll look like "C:\Program Files (x86)\Steam\Steam.exe" -noverifyfiles -nobootstrapupdate -skipinitialbootstrap -norepairfiles -overridepackageurl
put these commands on a steam shortcut and launch it that way -noverifyfiles -nobootstrapupdate -skipinitialbootstrap -norepairfiles -overridepackageurl then make sure steam doesn't auto-update or auto-open and you only open that shortcut