The block editor comes with a gorgeous distraction-free full screen editing mode. Enabling the full screen mode hides all of the WordPress menus, giving you space to focus on your content.
You can access the full screen experience from the editor settings and selecting Full Screen mode. The setting toggles the full screen mode. If active, the mode will disable. If inactive, the mode will be enabled.
To get back to the admin panel and exit the editing mode when you are in the full screen mode, just click on the logo in the top left corner. This will take you back to the content list.
Don’t forget to save your content before you exit.