set -s command-alias[100] get-over-here='choose-tree -w "join-pane -v -s %%"'
This is a quaint little command that will bring a pane(you can select interactively) to this window. You wont need it often but is such a time saver.
set -s : Server wide option (not just the pane, window)
command-alias[100]: add it to slot 100, 0-99 are already occupied!
choose-tree -w: Show all options of windows
join-tree -v -s: vertical split, s = source from this location
%%: Place holder for selection output.