There are enough open tabs in my PDF reader and left and right arrows appear in the top left and top right corner, respectively. If I open a new tab by double-clicking a regular item in the main window, the tab list doesn't scroll to the new active tab. Once some tabs are closed and the arrows disappear, the tab list will scroll to the new active tab when opening a new tab.
Though I can find the new tab in vertical tabs, the autofocus active tab is more appreciated and will enhance the user experience.