It should be possible to set a different password, used just for NX, with the help of password db. Unfortunately there’s a bug on Windows and we are currently fixing it. So watch out for the fix in the next update.
With the products that support SSH, you can use passwordless authentication with the help of SSH private keys. SSH support is only available in NoMachine for the Enterprise products right now.
For the free version of NoMachine, which authenticates using the NX service, passwordless authentication will be available very soon.