DarqUI also has a fullscreen windowed mode that allows you to mouse over to the other monitor. Look on the Settings page of the utility. If you use it, remember to go back into the in-game Options window and uncheck the built-in borderless fullscreen setting (and disable the setting in any other software).
You can add the private channel manually in the Window Manager. Open the browser with /browser and then click the blue gem button on the titlebar. Add the channel name in the slot, and check the box. Restart the game. You can also do this from the utility.