https://www.neowin.net/news/microsoft-brings-split-screen-to-all-edge-users-in-the-stable-channel/
Update the browser to the latest version by navigating to edge://settings/help.
Open edge://flags and search for the Microsoft Edge Split Screen flag.
Set the flag to Enabled.Restart the browser.
Click the Split Screen button on the toolbar and select the tabs you want to keep side-by-side. You can also launch Edge Split Screen by right-clicking a link and selecting Open link in split window.