Use the "View | Schema view" command or the toolbar button to switch to the JSON schema view (currently read-only) to generate a nicely looking tree diagram of your JSON schema. If the current JSON content contains syntax errors the text view will show the results of the well-formed check. You need to resolve all of them before you can activate the JSON schema view. You can expand and collapse parts of the schema to get a better overview of the JSON structure:
Use the "Generate JSON schema documentation (HTML)" command to create a new document in the editor which contains the generated HTML. The HTML documentation uses SVG to keep the diagram scalable to any size. After you have saved the document with the generated documentation you can open it directly in your browser.