What would be nice, is just something which clear the pending quantities (set to 0 or the delivered quantity) and (eventually save) the order. Yes it can be done manually but what you seem to not realize (do you ever use FA or just develop it) is some order can be really really big (in my case ...
SELECT count( * ) AS num
GROUP BY order_no
ORDER BY num DESC
LIMIT 0 , 30
Cancelling a partially deliver order of 200 items , meaning for each one, editing the line, setting the quantity to the delivered quantity, validating, waiting for the AJAX call to be finished etc ... is nearly 2s.
times 200 = 400 s, that's nearly 7 minutes of faffing around with the GUI just to cancel and order.
FA is great (and I'm really happy with it) but it's not really made manage big order (which is a shame because a part from little problems like that everything works perfectly).
(200 items in a order is only for sales order, if I look at my biggest purchases order I got: 495, 437 etc ... (and only because I split them, I'll get 2000 otherwise).