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;

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

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

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

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

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

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

FIG. 8 is a front view of the eighth image thereof;

FIG. 9 is another front view of the first image in a sequence for a display screen or portion thereof with transitional graphical user interface of FIG. 1 , but shown without the broken lines inside the screen for clarity of illustration;

FIG. 10 is a front view of the second image thereof;

FIG. 11 is a front view of the third image thereof;

FIG. 12 is a front view of the fourth image thereof;

FIG. 13 is a front view of the fifth image thereof;

FIG. 14 is a front view of the sixth image thereof;

FIG. 15 is a front view of the seventh image thereof; and,

FIG. 16 is a front view of the eighth image thereof.

The broken line showing of the display screen of FIGS. 1-16 and the remainder of the transitional graphical user interface of FIGS. 1-8 is for the purpose of illustrating environmental structure and forms no part of the claimed design.

The appearance of the display screen or portion thereof with transitional graphical user interface sequentially transitions between the images shown in FIGS. 1-8 and in FIGS. 9-16 . The process or period in which one image transitions to another forms no part of the claimed design.