Is it that plist, or is it /Users/xxx/Library/Preferences/loginwindow.plist as per item
~/ (tilde slash) is Unix/OS X shorthand for /Users/xxx so they are one in the same.
protip: ~ does not work inside quotes, if you are using them to protect spaces etc. "~/Desktop/My Stuff/file1.txt" won't work. For that sort of thing I suggest "$HOME/Desktop/My Stuff/file1.txt" instead
I work for the Department of Redundancy Department