How do I get the current "Highlighted" position?

I need this for a script in Editor Mode.

Basically, when I select an object, and I hold “V”, I can “snap” to the closest vertex. The vertex will be highlighted by drawing a gizmo in it.

How can I get the coordinates of that vertex in Editor mode?

The position of the gizmo is stored internally. But you can add a feature request for this information to be exposed:

http://feedback.unity3d.com/