### join the last active pane to the currently active window
bind-key j join-pane -s !
+### join the marked pane to the currently active window
+### ('bind-key m select-pane -m' is default to mark the current pane)
+bind-key J join-pane
+
### Move current window to session named "bg" (and create session if it does not exist)
bind-key B if-shell "! tmux has-session -t bg" "new-session -d -s bg" \; move-window -t bg