If you’d like to take advantage of as much screen real estate as possible, you can browse Vivaldi in fullscreen mode.
To go into fullscreen mode on Windows or Linux click on the Vivaldi menu > Window > Go Fullscreen or use the Keyboard Shortcut F11. On macOS click on View > Full Screen , use shortcuts ^ ⌘ F / F11 or use the Full Screen mode option on the toolbar.
Furthermore, you can toggle the UI visibility by using the keyboard shortcut Ctrl F11 / ⌘ F10. It’s also possible to hide individual UI elements like the Panel or Address bar with Keyboard Shortcuts. You can set and edit shortcuts for each toolbar in Settings > Keyboard > View.