It's quite a frequently used part of the Orders tab and by not having this with a keyboard shortcut slows down our agents a little.
Having a shortcut for "Load Last Orders" would be incredibly helpful!
This is not a direct hotkey like you are asking for but just in case: Alt-O+L works. Alt-O opens the Orders menu and then "L" loads last order from that menu. Once you get the hang of it, it starts to feel like a hotkey! :-)