Ability to resume editing from last position / track last edited sections

When a user closes the app and returns later, they should be able to start writing again from the section they edited last. Similarly, if they are working in one section, and change something in another section, when they are ready to resume they should be able to track where they edited last so they can continue. This is specifically useful for revision sessions.

Current work around:
Highlight the last section edited in red so the user can visually spot where the last edited position.