Ideally with Microsoft Windows it'd be the user's "AppData\Roaming", but even a subfolder of a game's root would help.

As it is sync'ing my save games is a bit of a chore as it requires either explicitly chosing them after they're created or moving and symlinking to a sync'd folder.

My guess is such work could be done even without the source by binary tweaking it.

It'd be nice if GOG also provided options for syncing save games. Even if just using Dropbox as an install or setup option.