Looking at the bytes

A plugin can read and rewrite the file at the section level through api.document.sections (src/editor/sections.ts): currentChk serialises the open scenario — dirty sections encoded, everything else byte for byte — and parses the result back so every occurrence has its offset, and a raw edit mutates that ChkFile and parses a fresh Scenario from it, which replaceScenarioAtom installs in place of the open one. The Section Explorer plugin (listed by default, off until ticked) is the annotated hex editor built on that: every section with what the registry knows about it, its bytes coloured by field, and the meaning of each value.