monaco-editor version: 0.26.1
Browser: N/A
OS: N/A
Playground code that reproduces the issue: N/A

The following TypeScript code:

window.MonacoEnvironment = {};

Yields:

Property 'MonacoEnvironment' does not exist on type 'Window & typeof globalThis'.

window.MonacoEnvironment isn’t defined by the type definitions, only the global MonacoEnvironment is.