Add a multi-annotation review mode for existing Markdown files

What feature would you like to see?

Add a first-class annotation review mode for existing Markdown files opened from the Codex Desktop sidebar / Project Preview.

The user should be able to:

1. Open any existing local .md file from the sidebar.
2. Select a passage in the rendered Markdown preview and attach an instruction.
3. Repeat this for multiple non-contiguous passages without sending a new turn each time.
4. Review, edit, or remove the pending annotations.
5. Submit all annotations to the active task in one action.
6. Have Codex apply the requested edits to the original Markdown file.

Each annotation should carry a stable source anchor back to the original file, such as:

• file path;
• source line/range;
• heading and block identifier as a fallback when rendered and source positions differ.

An explicit Open with annotations or Annotate action would also work if the normal sidebar preview needs to remain read-only.

Why is this useful?

My concrete use case is revising a long-form article with many changes across the document.

Without multi-annotation support, I have to write a numbered list in the composer and manually describe both the requested change and the location of every passage. For a document with many edits, location descriptions become repetitive, ambiguous, and much slower than the actual editorial feedback.

The value of annotations is that the selected content already communicates where the instruction applies. Queuing multiple annotations before sending them is important because article review is normally completed as one reading pass, followed by one coherent revision pass.

Desired workflow

Open existing article.md from sidebar
    -> enter annotation mode
    -> select passage A and comment
    -> select passage B and comment
    -> select passage C and comment
    -> review "3 pending annotations"
    -> submit all to the active task
    -> Codex edits article.md
    -> user reviews the resulting diff

Useful details:

• The Markdown preview should remain rendered while annotating.
• Pending annotations should be visibly marked in the document.
• The user should be able to edit or delete a pending annotation before submission.
• All annotations should be sent as one structured batch, not flattened into manually numbered prose.
• The feature should work for files that existed before the current task, not only newly generated artifacts or changed lines in a Git diff.
• A raw-source annotation view could be offered when precise Markdown syntax matters.

How this differs from related issues

• #25371 is a bug report about the contextual selection menu no longer appearing in Project Preview. Restoring one-shot actions such as Add to conversation does not provide a queued, multi-comment document review workflow.
• #26931 concerns inconsistent PDF annotation availability depending on how a PDF is opened.
• #35918 requests inline comments on Plan mode plans.

This request is specifically for a reusable, multi-annotation review mode for existing Markdown documents.

Environment

Observed in Codex Desktop on Windows with package OpenAI.Codex 26.730.8199.0, but the request is platform-independent.