editorLayout

# recording.editorLayout/layout.yaml
title: The scene and the first agent's terminal side by side.
mode: full            # full | simple
panels:
  - { id: viewport, dock: center }
  - { id: agent, dock: right }
fractions: { right: 0.42 }

A layout the editor ships lives in the built-in library; one a person saves lives in the world at /zero/source/editor/layouts/. Both are the same asset, and a world layout of the same name stands in for the built-in one.