I assume you are asking about two users connecting to the same virtual desktop session? By default, users connecting to a host where a NoMachine Terminal Server product, e.g Workstation, has been installed can share their NoMachine virtual desktop with other users.
If one of the two users has already created the virtual desktop session, the other user can authenticate and select “All desktops”. The list of available sessions will be shown. See the screenshots I have attached.
Further reference:
How to share a NoMachine virtual Linux desktop with other users
https://www.nomachine.com/AR07P00993