Hi,
In the file show_block_cart.php, that you can edit via the menu Display>Views, you'll find this piece of javascript code:
window.hikashop.checkQuantity(this);
That's what you have in the "onchange" attribute of the quantity input field in the cart view of the checkout.
So you can add after it such code:
if (this.value != \''.$product->cart_product_quantity.'\'){'.$input.'return window.checkout.submitCart('.$this->step.','.$this->module_position.'); }
That will refresh the cart view.
Note however that it is in an onchange event.
So after you changed the value, you need to click elsewhere to validate the change. Otherwise, if we were submitting the data as you type, you wouldn't be able to enter numbers higher than 9 in it as it would submit the data right after you pressed the first digit.
Or it would require a waiting time, but it could be different from one person to another.
So it's better to have it on "onchange" I believe.
In fact, the code modification I'm proposing above is what will be in the next version of HikaShop.