I found a similar request from October of '19 but I thought it was unrealistic to have it mapped to a remote button. How about having the "return" button (left arrow on a Shield remote) have it hit a "return to top" selection before it hits the slide-out list of menu items?
Or even have the left D-pad actually have "return to top" as the top item in the list instead of favorites?
Why you ask? With Pluto channels added, it takes some going to go from the bottom of the grid to the top, where my OTA channels are.