Microsoft is rolling out the new Vertical Tabs feature to users in the Dev and Canary channels. Once enabled, this feature will move the tab bar from the top to the left side in a vertical layout. You can switch to the vertical layout by clicking on the button located at the top left corner. The feature is aimed at users with dozens of tabs open at any given time. Microsoft Edge was first released in January 2020 and is getting better every month with new releases. It is likely to go live in Microsoft Edge stable channel later this year.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-edge-gets-vertical-tabs-feature-you-wont-find-in-chrome/