How can I edit saved games in Civ V? [closed]

Nope. Not that it's not possible, just no one ever made one (IIRC, there was a save editor for pre-expansion Civ4, but nothing afterwards)

However, there is a mod that lets you edit many many things ingame (eg/ terrain, techs, diplomacy, etc) that probably covers most of what you would want.

IGE