The Rendered view: Ctrl+T
Under autodoc --gui, Ctrl+T switches the page between its Raw view, the Markdown as written, and its Rendered view: the headings at their sizes, the marks hidden, tables, code and Mermaid diagrams drawn.
flowchart LR R[Raw, the Markdown] -->|Ctrl+T| D[Rendered, as it reads] D -->|Ctrl+T| R
The Rendered view is still the editor. Every line is editable: the line under the cursor shows its Markdown, the rest show what they make. Ctrl+T again goes back to Raw.
HTML files ask how to open: Simplified, their text read-only, or Raw, the HTML itself to edit and save. A raw HTML file's Rendered view is its page, drawn natively with its own stylesheets and images: j k scroll, its links open notes, files and the browser.
File › Preview HTML (SPC H) opens the note's page beside the editor, live as you type.
The right-click menu: Undo, Redo, Copy, Cut and Paste, View diagram, Go to link, Back, and in the GUI the Zoom. From the keyboard: Shift+F10, the Menu key where your keyboard has one, or SPC ..
A terminal has no Rendered view: there the page stays Raw.
More: Reference, Chapter 4: Rich Authoring, Embeds, and Export.