While trying to fall asleep, I ended up thinking about the key combinations used to create splits in tmux.
You know. As one does.
By default, you use Ctrl-b % to create a vertical split (i.e. two panes side by side). A horizontal split (one pane on top, one pane on the bottom) is Ctrl-b ". It seems a common remapping is to change these to Ctrl-b | for vertical, and Ctrl-b - (or Ctrl-b _, or both) for horizontal. These make more sense at first glance: | and _ look more like the end result more than % and " do. % kind of looks like two panes side by side, though it could also just be two panes stacked; " would definitely be two panes side-by-side, though.
So if it’s not visual, what’s the mnemonic for these defaults?
Oh. % splits the pane down the middle, and it’s located in the middleish of the keyboard, almost splitting the two halves from each other. " splits across the pane, and it’s on the middle row if you ignore the function keys. In between the top and bottom halves.
Alright. That’ll do.