Display screen or portion thereof with transitional graphical user interface

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

FIG. 2 is the second image thereof;

FIG. 3 is another front view of the first image thereof, showing only the claimed features, separately for clarity of illustration;

FIG. 4 is another front view of the second image thereof, showing only the claimed features, separately for clarity of illustration;

FIG. 5 is a front view of the first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design according to a second embodiment;

FIG. 6 is the second image thereof;

FIG. 7 is another front view of the first image thereof, showing only the claimed features, separately for clarity of illustration; and,

FIG. 8 is another front view of the second image thereof, showing only the claimed features, separately for clarity of illustration.

The thicker dashed lines shown in FIGS. 2 , 4 , 6 , and 8 form part of the claimed design. The outer perimeter shown in broken lines in the figures illustrates a display screen or portion thereof and forms no part of the claimed design. The remaining broken lines in the figures illustrate portions of the graphical user interface that form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 - 2 and 5 - 6 , respectively. The process or period in which one image transitions to another image forms no part of the claimed design.