Show pane numbers
panes
// what it does
Ctrl+b q (display-panes) briefly overlays each pane with its index number so you can read the layout at a glance. The numbers vanish after display-panes-time (default 1 second). It's mostly used right before selecting a pane by number.
// shortcut
Ctrl + bq
// gotcha
The overlay disappears quickly; if one second isn't enough, raise display-panes-time. The numbers are pane indexes, which can change as you split, kill, or rotate panes.