Double clicking the saved message in the Drafts folder should open it again in the same state that it was in prior to being saved as a Draft, i.e. it can be edited. As this appears not to be happening in your case, it might be worth reinstalling Windows Live Mail. I have WLM 2011 and its messages saved as Drafts behave as I'd expect and can be edited.
"Suggestions on Google to double, or right-click to open it, or move to inbox"
Moving to "Inbox" isn't a good idea as it would then behave as a message you've received and the contents couldn't be edited.