tmux is a great tool if you live in the shell. Sometimes you'll need to copy-paste between windows & panes. If you have a vertically split window, you can't use the mouse to copy text from one side to the other.
Here's how to copy-paste between tmux windows or panes:
ctrl+b,[allows you to move your cursor around
ctrl+spacestarts copying from where the cursor is
ctrl+wgrabs the selection to the tmux clipboard
ctrl+b,]pastes the clipboard out to the current window / pane
That's it, hope it helps you!
If this helped you, follow me on dev.to for more tips. I use dev.to as a journal, where I record any tricks that I see myself using regularly. You'll probably find it useful too!