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Automatically add and delete control points and links. This icon lets you run both tasks above Cette icône permet de réaliser en une seule fois les tâches des deux icônes précédentes. 

As you see, some French text has been left behind - another day I would have a go at the translation, but today...

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I have just applied changes to the geometry analysis text: note the heading of this section differs from the label of the button/icon in the CP Editor; that label speaks of 'geometry editor'.