To say "the editing" in english makes no sense on its own, but it would as part of a longer sentence where the "edit" part refers to the verb To Edit. "The editing session lasted for hours", "Where is Joe? He is busy editing the video". "editing" is not a noun, so if I saw this as a sentence (La edicion) I would simply answer The edition. I am curious if you answered "the editing" if it would be accepted.
Actually, editing is a noun. I'm not sure whether Duolingo allows links here, but you can see it on the American Heritage Dictionary. One could say, "he took care of the editing for me."