I hold a large ammount of private Blueprint Catalogs, all of them cost me a lot of effort.
But because its so easy to alter or remove stuff in blueprint books, without any warning, i never feel like my blueprints are "safe" nor final / complete.
This actually becomes a problem with larger books, because small removals/alterations tent to be overlooked.
It actually makes me pretty paranoid about my blueprint books, and i tent to save the Strings in a .txt file in a non game folder.
Being able to make readonly books will not only feel safer, it will also live up to my sense of completion
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Personally i would like to see a little lock icon in the Blueprint book screen (next to the pen to alter name).