One of those things wube should fix very fast. I think about moving this to bugs, because it’s unexpected behavior; what do you think? The possible explanation why this isn’t working as expected: Factorio was for a long time not invented to play it under Steam, the main focus was to sell it directl...

IIRC issues with it deleting blueprint libraries is why it isn't on by default. Steam's cloud sync isn't great, and even the save one loves to delete saves. As long as you have a save file from before the library was deleted you can still get your blueprints back: https://forums.factorio.com/viewto...

Game with so many QoL doesn't have this option marked as default on. Why? Now i lost so many HOURS of playing only for improve advanced blueprints only to find out this option deleted my blueprints. I'm taking break of this sad joke.