It cannot kill the window only. If you execute a command that never returns, it breaks whole session.
You can see the output, when you move the window away, cannot you?
I do not know netparm command, but cannot you execute it in a way that it returns?

this window gets in the way. I am prompted to hit return in the command dialogue to see more information (netparm command).
I can't do this as the window is in the way,.
Instead I hit the X to kill the window and it terminates my session. Perhaps this should just kill the window and not the session?????

Also the option to turn off the buffer optimisation seems to have no impact. Maybe my crappy system though.

However this is a very useful tool. Thanks for everyone's efforts.