This is not currently possible, but is planned for a future release.
In the current version, when the user has multiple monitors on the client, it is possible to choose if the NoMachine virtual Linux desktop session has to be spanned on all monitors so that the virtual desktop sees this as one giant monitor, or if each monitor can be treated as an individual monitor. The difference is in the first case when you for example maximize a window, it spans on all monitors. In the second case separate monitors let you drag windows between monitors. Maximized applications only span one monitor.