Just to note, splits in tmux and screen behave differently. iirc, in screen you have a set of splits and fill them in with different ports (kind of how vim thinks of viewports). so technically you can have the same viewport open twice on your monitor and the other will mirror the workings of the one that your are working in right now. in tmux each 'tab'/window is a set of splits, which act more like sub-windows, and don't really share across multiple spaces.