There isn't an individual flag for edits: we can't use a special flag relating to someone who edits a post of another user. Now the only way to draw a moderator's attention about someone's edit is to use that flag which is under the post they edited. Placing the extra flag inside the edit block will increase the number of complaints to moderators about useless and bad edits. This will increase the responsibility of those users who will want to edit others' posts.
I suggest to do a flag button inside an edit block:
P.S.: there is my first topic which can be considered as an introductory part for this question.
update (about being a dup):
The answer suggested to me is Is it possible to flag an edit for abuse? which is about asking what to do and my post about suggesting what to do. So they are not duplicates.
There is the answer Add the ability to flag an edit for moderator attention which can be considered the same as mine (although mine raises a global issue about how to increase responsibility of people). You can suggest it as a dup if you think it's necessary.