Umm.. I have no idea where a 'task view' button is. (I'm still in Win7)

I do have my task bar & browsers address bars at the top. It just 'feels' right...(even though some programs have hard coded defaults to open in the upper left corner.)
I just managed to activate a 'task manager' in Vivaldi by rt. clicking on the address bar and selecting it, it doesn't show much of interest. There are "sub-frames" listed, and several open tabs... perhaps this new extension is hiding some?

Modern browsers and operating systems have so many options and alternate ways of doing things that even a "menu freak" like me, doesn't
find them all. I can tile my open tabs in several ways, but I almost never do, as tabs serve the purpose... and scrolling thru tabs suits me.

YMNDD (Your mileage no doubt differs)