Having being a `screen` user for over two decades, migrating to tmux has been a pain. A week ago, however I discovered a wrapper called `byobu` (1) which really helps, and controls both screen and tmux depending on which one you have on your system. It basically wraps Function keys and more to tmux, but has plenty of other features. Time will tell if it was worth installing, but I do believe it's simpler for me to use it as a transition from screen.

(1) https://byobu.org