For me tmux is everything. But I have been looking for 2 utilities they may not exist.

- tty keystroke router: A program that lets you send keystrokes to different tty's (ideally tmux sessions) but not taking over the actual terminal (so sort of a background application , a daemon that listen to a certain key bind and upon pressing it will route all the keypresses to a certain tty/tmux session.

- tty screen real estate extender: Basically be able to link one tty (tmux-window) (attach to it) from two different terminals. These two terminals one of them will be displaying the first N columns second terminal attached will be displaying from N till width of the tty (so you can hook up two monitors and widden your ttys)