Having a create order button on the back end is not that simple as you also need to have a way to select the products, the user, his address(es), a possible coupon, a payment method and a possible shipping method.
So there is a lot involved that just adding a new button. Of course, you could also have just the new button create an empty order and then have the admin enter everything by hand with the interface already available but that means that you have to enter the name of products yourself, you have to enter the price yourself etc... It's a lot more complicated for you than doing it from the front end.
I'm still not sure what would be the better way to implement that while keeping it simple enough to implement. If you have suggestions...