I know I’m a bit late to the discussion, but I’ve discovered a way to clean up the Steam Cloud that might help anyone whose cloud storage is overfilled and causing other issues:
Unfortunately, the game client doesn’t expose all cloud-stored files. Some remain hidden and never appear in the usual folders (User/Game or InstallDir), which seems to be an oversight by the developers.
When I visited
https://store.steampowered.com/account/remotestorageapp/?appid=813780
I found numerous files kept in the cloud that had never been downloaded to any AoE2 game folder and don’t show up in the game client.
Fortunately, there’s a third-party tool for Steam:
https://github.com/GMMan/SteamCloudFileManagerLite
(see also https://github.com/GMMan/SteamCloudFileManagerLite/issues/23 for step-by-step instructions. (Game AppID: 813780))
It lets you manually delete those unwanted cloud files.
To the developers: please ensure the game state is fully synced with the cloud and don’t omit any files (even outdated ones), so users can manage their data without relying on third-party tools.