We seriously need a button at the bottom of the page that says "Top"

click the home button

like hitting the 'home' button inside the browser window? it's keyboard and not really much help on tablet/phones, but it's something.

ctrl + up-arrow and you're done.

I agree, I have run out of Desk to scroll so far down and back up again. I need a new desk.

click the x on the tab and open again?

It may depend on instrument and OS, but on mine (PC and MS 'Windows') it's the [Ctrl] + [Home'] combination for almost all programmes.

or just hit the home key?

honestly, the entire keyboard doesn't need to duplicated in website interfaces

They would mess it up and put it on top