The Fill button fills everything up to that point. So if you click 5 rows down, it will sum it all up for you.
I can't do that until the cost calculator becomes order book aware. That's why the costs are "estimated". Because there's no guarantee that the order gets filled at exactly what you plug in. On a Bid it could get filled lower, and on an Ask it could get filled higher. Keep in mind that the order book is constantly changing in the background.
I guess I could do an "estimated total"? But honestly, I'd rather not have more rows and the ~0.002x fee isn't going to play into the costs much when looking at what is already an estimate.
Cheers.