Octave transfer, Hoherlegung/Tieferlegung. A shift of a note or linear progression from one register to a higher or lower register, usually for some aritstic or contrapuntal purpose. At deeper levels, such transfers represent motions away from the obligatory register.
In the example, from Variation 22, notes of an inner voice are shifted up one octave, above the main linear progression. The octave transfers are indicated by broken diagonal lines.