I don't know if this would qualify as a feature request because it's more about cosmetics than feature. However putting tabs on the left of the page means using the screen space less efficiently. Imagine browser's tabs on the left of the screen and you'll understand. It's so much more meaningful to put them on top and help people to browse through tabs while allowing them use lef-right span more efficiently.
It would also not take a lot of time I suppose.
