<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=348784) </details> <!--IssueSummary end--> As an iterative step to approach full support of document outline when working with markdown files in the single-file editor or WebIDE, this step is about introducing the code outline when **live-previewing markdown** files in Source Editor