Vertical tabs are meant to help users see and manage multiple open tabs more easily. I'm excited about this feature, given I routinely have at least a couple dozen tabs open in my browser.
To try out the feature, testers just need to click the vertical tabs icon, which is in the top-left corner of the browser. To switch back to horizontal tabs, users can just click on the vertical tabs icon again. Testers can reorder and manage multiple tabs at once; mute noisy tabs by clicking on the speaker icon; and pin favorite tabs. Users can make the vertical tabs pane smaller by clicking on the arrow icon in the tabs pane.
The Edge Dev channel gets new test builds weekly. Microsoft hasn't yet said when vertical tabs should be coming to the Stable/mainstream user channel, but I'd think by late this year or early next, the feature should be live.
Microsoft announced 'Sleeping Tabs' for Edge feature in September -- which is aimed at cutting CPU and memory use. And this week, officials shared information on a coming Startup Boost feature it's planning for Chredge which will help the browser start more quickly. Startup Boost will be an optional feature in Edge version 88.