From 3.2:

* Add a -S flag to new-window to make it select the existing window if one
  with the given name already exists rather than failing with an error.

It would be great if that flag had that effect with -t target-window too, so that these nifty bindings could work (jump to a window if it exists, creating it if necessary):

bind-key 1 select-window -S -t 1
bind-key 2 select-window -S -t 2
bind-key 3 select-window -S -t 3

I'm assuming there is currently no (easy) way to do that. I have tried new-window ... \; select-window ..., but as documented the sequence is interrupted if a command fails, so no dice.