Can I edit or refill my order, and what happens if I cancel my order?[/b]
Yes, you can edit your order. You can increase order price and optionally limit hashing power (or change existing limit). If you edit your order and set higher price, the logic is the same as when submitting new orders, see also How can I buy hash power at NiceHash?

You can also refill your existing orders which essentially extends the running time of an order - you can refill your orders as many times as you want and you are not additionally charged for refilling an existing order.

You can also decrease price of your existing orders. To avoid manipulation, price decrease is only available within predefined price steps, can be applied only each 10 minutes and resets your position to the bottom of sub-list of same-priced orders. The predefined value of price decrease is displayed on Decrease price button. Of course, once you decrease price you can always later increase it without any limitation.

If you cancel the order, you'll get your Bitcoins back. This enables you to quickly switch between different algorithms (Scrypt/Scrypt-Adaptive-Nfactor/SHA256/etc.) in dependence of current profitability without loosing funds or hash power.

The remaining Bitcoins that have not been used yet for paying accepted shares are loaded back into your wallet and service fee will be refunded (from the remaining Bitcoins), however small 0.0001 BTC non-refundable order submission is not refunded. We've had attacks with order spamming in the past and currently don't have any other appropriate ways to prevent order spamming. Our first priority is to protect all users, stability and security of the system. Thanks for understanding.

Please note: it takes a couple of minutes for the refunded funds to appear in your NiceHash wallet.

Note: You can not lower the price on your order and order can not be paused. These features would lead to orders manipulation or abuse (discussed above) and are thus not available, but you can implement them by canceling and re-submitting orders, applying to the above stated rules.

ETA use to be available for all orders but, NH removed it because they felt it gave too much information about the BTC balance of the order.
I was told it was a standing request by many users.

https://bitcointalk.org/index.php?topic=562238.3625

But I do have to say I miss it as well.

1st block of the day