A mod for editing/updating/modifying, existing blueprints without placing them in to the world first.
WARNING! This mod is in development, and not yet fully tested.
It is strongly recommended, that before using this mod, you back up your blueprints in the Factorio library, in a separate save.
That way if anything goes hideously wrong, you can load that save, and get all your BPs back intact.
Feedback / bug reports appreciated