Instead of changing settings file, I use the -p command line option to specify the port. I also use nssm on windows for multiple instances. So each service launches for example...
node-red -p 1881 -u c:/nr1881
-
node-red -p 1882 -u c:/nr1882
And so on.
BTW, @knolleary that document you linked to doesn't show the -p option or -t option.