The act of taking a pane within a window and moving it to its own window is called breaking that pane. It can be accomplished with the tmux command break-pane or the keys <Prefix>, !.
By default, the break-pane command will operate on the currently selected pane; however, any arbitrary pane can be specified using the same syntax we saw in the previous example to select a window within a session, specifically separating the session and window name by a colon. However, of course, a pane also has an index, which can be added after the window separated by a period. This all sounds complex, but it is actually rather intuitive.
For example, to select pane 2 in window 1 in the session Advanced and break it into its own window, we could use the command break-pane -s Advanced:1.2.
Note
Remember that you can see the current pane indexes flash on the screen briefly with the key binding <Prefix>, q.
When you break a pane, tmux automatically switches the window to select the window...