How to swap one large tmux pane with several smaller ones?

How do you swap one large tmux pane with several smaller ones?
In other word: from an arrangement like A – to an arrangement like B:

                  AB
      ┏───────────────────────┓         ┊         ┌───────┬───────┬───────┐
      │                       │         ┊         │       │       │       │ 
      │           1           │         ┊         │   2   │   3   │   4   │
      │                       │         ┊         │       │       │       │
      ┡───────┬───────┬───────┩         ┊         ┢───────┴───────┴───────┪
      │       │       │       │         ┊         │                       │ 
      │   2   │   3   │   4   │         ┊         │           1           │ 
      │       │       │       │         ┊         │                       │ 
      └───────┴───────┴───────┘         ┊         ┗───────────────────────┛

There are plenty of resources covering similar operations, but not quite this.

  • / / / moves the focus to another pane.
  • alt + / / / adjusts their dimensions.
  • Space cycles various pane layouts / arrangements.
  • { / } shoves individual panes left / right – but that just forces a direct swap, like:
                  AC
      ┏───────────────────────┓         ┊         ┌───────────────────────┐
      │                       │         ┊         │                       │ 
      │           1           │         ┊         │           2           │
      │                       │         ┊         │                       │
      ┡───────┬───────┬───────┩         ┊         ┢───────┱───────┬───────┤
      │       │       │       │         ┊         │       │       │       │ 
      │   2   │   3   │   4   │         ┊         │   1   │   3   │   4   │ 
      │       │       │       │         ┊         │       │       │       │ 
      └───────┴───────┴───────┘         ┊         ┗───────┹───────┴───────┘