The sidebar is one of the most overlooked aspects of Opera. However, it plays a key role here. Apart from permanently pinning the sidebar for quick access to your history and bookmarks, you can also install sidebar apps and also include web apps for WhatsApp, Telegram or Facebook Messenger. While the latter comes installed out-of-the-box, you can download more add-ons that support the sidebar functionality such as Google Keep, Instagram, and other similar apps. To install new sidebar apps, go to the Opera extensions store and click the Sidebar link.