How to save yours blueprint?

Press win + R and write %appdata% go to roaming>factorio. Your file is blueprint-storage.dat (for vanila) blueprint-storage-2.dat (for dlc space age)

Problems with synchronization.
I understand that the game prioritizes saves from steam cloud. Therefore, if you have the correct file in the folder, but no blueprint. Turn off steam cloud and enter the game.

To fix file synchronization, you can try this. Go to the folder where the file with the drawings is located. Delete/drop it into another folder so that steam creates a new file of your blueprints in steam cloud

Steam>userdata>ur user id>game id>blueprint-storage-2.dat.zstd

Factorio id = 427520
User id
Open your profile and on the top left there will be a link to your profile where the id will be

https://steamcommunity.com/profiles/00000000000000000/