The following entities can be made protected, via their isProtected flag:
isProtected
Developer's Guide
Dependency Management
Adding a new client library
Having a simpler packaging system
Building and deployment
Documentation
Running a development build
Build deliveries locally
Releasing a version
CI
Main
Project maintenance
Updating dependencies
bettersqlite binaries
Node.js, Electron and `better-sqlite3`
Testing compatibility
CKEditor
Environment setup
Building & updating
Differences from upstream
Development and architecture
Internationalisation / Translations
Guidelines
i18n-ally
Live reload
Themes
Synchronisation
Content hashing
Build information
Database
attachments
attributes
blobs
branches
entity_changes
etapi_tokens
notes
options
recent_notes
revisions
Protected entities
Deleted notes
Special notes
Branch prefixes
Revisions
Backlinks
Note types
Safe mode
Scripting
Widgets
Right pane widget
CSS