The Blog Settings section in the Studio 9 theme Customizer contains 6 options. Navigate to Appearance → Customize → Theme Options → Blog Settings to access these settings.

Options

• Post Thumbnail Size (Select) — Choose thumbnail size (large, cropped, small, or disabled).
• Breadcrumbs (On/Off) — Enable or disable breadcrumb navigation.
• Breadcrumbs Categories (On/Off) — Show or hide categories in breadcrumbs.
• Single Post Thumbnail (On/Off) — Show or hide thumbnail on single posts.
• Post Sidebar (Select) — Sidebar position for posts (left, right, or none).
• Page Sidebar (Select) — Sidebar position for pages (left, right, or none).

After making changes, click Publish at the top of the Customizer to save your settings.