Complex sentence: When the UI is shown, the tabs are listed on the top of the screen, with small previews of the webpage on each tab, and a button to add a new tab is placed in the top-right corner.
Split into simpler sentences: When the UI is shown, the tabs are listed on the top of the screen, with small previews of the webpage on each tab. A button to add a new tab is placed in the top-right corner.