tmux - What does bind-key -r mean?
Solution 1:
Quoting the TMUX(1) manpage:
The -r flag indicates this key may repeat, see the repeat-time option.
And a quick search for repeat-time yields this:
repeat-time time
Allow multiple commands to be entered without pressing the prefix-key again in the specified time milliseconds (the default is 500). Whether a key repeats may be set when it is bound using the -r flag to bind-key. Repeat is enabled for the default keys bound to the resize-pane command.