Display screen or portion thereof with transitional computer graphical interface thereon

FIG. 1 is a front view of a display screen or portion thereof with transitional computer graphical interface thereon showing a first image in a sequence of a first embodiment according to the claimed design;

FIG. 2 is a front view of a second image thereof;

FIG. 3 is a front view of a third image thereof;

FIG. 4 is a front view of a fourth image thereof;

FIG. 5 is a front view of a fifth image thereof;

FIG. 6 is a front view of a sixth image thereof;

FIG. 7 is a front view of a seventh image thereof;

FIG. 8 is a front view of a display screen or portion thereof with transitional computer graphical interface thereon showing a first image in a sequence of a second embodiment according to the claimed design; and

FIG. 9 is a front view of a second image thereof; and,

FIG. 10 is a front view of a third image thereof.

The appearance of the transition is sequential from FIG. 1 to FIG. 7 in the first embodiment, and from FIG. 8 to FIG. 10 in the second embodiment. The process or period in which an image transitions to another image forms no part of the claimed design.

The shading is part of the claimed design. The outermost broken line illustrates the display screen and a boundary and the remaining broken lines illustrate portions of the transitional computer graphical user interface. None of the broken lines form part of the claimed design.