nope, it just sets an environment variable the the device manager uses to change the function of the "Show Hidden Devices" flag to basically show all hidden and disconnected devices. If you type set by itself, it'll show you all the environment variables, and it will be there.

You have to run devmgmt.msc from the same command window though, because that environment variable is not system wide (unless you make it so), and is destroyed when the command window is closed.