The least valuable & final planned feature was the row/column shifting.  These 4 operations of such lethal cunning were the only way to synchronize with shifting operations in the spreadsheet.  Goog sheet labels the columns letters & the rows numbers.  After Z, it goes to AA, AB, AC.  For even the most insane financial calculation, the lion kingdom would only go to Z so that was the plan. 

Thus, there was a simple test form.  Helas, the shifting operations get really slow.  There definitely needs to be an hourglass or status symbol.

After so many years of writing web apps, the lion kingdom finally remembered the tool box should go on top.  Somehow, the browser tripped up that convention.  It more easily allows the canvas to fill the window.

Maybe lions got nostalgic for early 80's graphics programs. 

There's bugger all footage of those early graphics programs, but up to at least 1983, they tended to put menus & command lines on the bottom.  The way the Images Paint System drew a palette right over the bottom looks hacky now but it was pretty slick in the day.  PDFMerge is about as primitive as those early graphics programs.

Another idea was keyboard shortcuts for undo, redo, save, delete, cut, copy, paste, next page, prev page, zoom, select all.  Key trapping in javascript is a difficult thing.  You have to seek out every place a key could be trapped & manually disable it, replacing it with your own event handler.  Text boxes need different event handlers than canvases.  It's not like there's a concept of a top level event handler & returning true traps the event.

It looks like goog sheet itself only traps pgup, pgdn in some widgets but not all.