This command removes every blueprint that has been placed in the game. Blueprints are commonly referred to as ghosts - they are the outlines of buildings that appear which you add resources to.
The syntax for the cancelallghosts command is as follows:
Find below working examples of the cancelallghosts command.
This is the only way this command can be used. Running the above command will remove all blueprints you have previously placed - note that this is undoable.