I have a similiar need to close channel windows where I am unable to get the part message from the IRC server. When not actually in the channel but connected to IRC I only get "your not on that channel" instead of it sending a part message which will then automatically cause mirc to close the channel window. It obviously isn't difficult to close the channel manually with a click but this would help in other remote areas like bots and such if I were able to /window -c #channel or something like that. Though the help file does say /window is to "allows you to create and manipulate custom windows" I wish there was something that could be done here.
