I don’t use panes in iTerm often enough and whenever I do I seem to have forgotten the keyboard commands to split and navigate them, so…
- ⌘D – Split vertically
- ⌘⇧D – Split horizontally
- ⌘⌥↑ (or ↓, ← or →) – Navigate between panes
- ⌘⇧↩ – Maximise pane toggle