How to add more map windows?

There is a nice "Character Selection" option in File menu that will be a great use to me these days when boxing. But for now I am struggling how to make both boxes up all the time? I mean I Want to hear the voice alerts when soem rare mob spawns either on one box or another. And for now it seems I can only have either 1st character selected or 2nd. But how can i have both (or more) characters being monitored? Maps window area seems to be prepared to handle more than 1 map at the time - there is a tab with map title and room for more tabs I mean. I also found out that standard keystroke CTRL+F4 closes the window. But I failed to find a keystroke to add additional windows/tabs there. Any hints please?