Help is on the way! To mark it as solved, use the /solve command. In the meantime, here are some existing threads that may help you:
Documentation:
- The Payload Config - Compatibility flags
- Slate Editor
- Rich Text Editor - Extending the lexical editor with Features - Integrating New Features
- Lexical Migration - Migrating lexical data from old version to new version
- Rich Text Editor - Extending the lexical editor with Features