ok, I found an answer to my own last question...

while "LAUNCH" program does not have a method to enter copmmands and therefore cannot (apparently) add new users, one can instead run "OpenSim.32BitLaunch" and you will get a "dos type dialog" where you can then enter the standard "create user" command

not sure if this is the best way to do it, but it works (as far as I can see so far... I just created the user, haven't treid to log in to my standalone as the new user yet.... )

Hopefully this helps