FWIW, I've switched to tmux but think tmux's implementation of split screen is broken and desperately miss screen's. Screen lets each part of a split screen se

FWIW, I've switched to tmux but think tmux's implementation of split screen is broken and desperately miss screen's. Screen lets each part of a split screen select a different existing window. Tmux makes both parts of a split part of a single window, so you can either have two things going in one split, or have something else going on in another window, but if you suddenly decide you want two existing windows side by side, you can't do it.