It seems that the Microsoft Edge browser has changed a bit, and when I look closely, there is a ‘Vertical Tabs’ on the left (2021. 3. 10.). You can remove the ‘Vertical Tabs’ by clicking the icon at the top of the’Vertical Tabs’.
These days, the width of the monitor is longer than the vertical, so I think the ‘Vertical Tabs’ is efficient in terms of space utilization. I’m also using the windows taskbar vertically (right).