Display screen or portion thereof with transitional graphical user interface

FIG. 1 is a front elevation view of a first embodiment of a display screen or portion thereof with transitional graphical user interface, showing a first image of our new design;

FIG. 2 is a second image thereof;

FIG. 3 is a third image thereof;

FIG. 4 is a fourth image thereof;

FIG. 5 is a fifth image thereof;

FIG. 6 is a front elevation view of a second embodiment of a display screen or portion thereof with transitional graphical user interface, showing a first image of our new design;

FIG. 7 is a second image thereof;

FIG. 8 is a third image thereof;

FIG. 9 is a fourth image thereof;

FIG. 10 is a fifth image thereof;

FIG. 11 is a front elevation view of a third embodiment of a display screen or portion thereof with transitional graphical user interface, showing a first image our new design;

FIG. 12 is a second image thereof;

FIG. 13 is a third image thereof;

FIG. 14 is a fourth image thereof; and,

FIG. 15 is a fifth image thereof.

The bold short-dashed broken line forming a circle or portions of a circle in FIGS. 1-4, 6-9 , and 11 - 14 are part of the claimed appearance of the transitional graphical user interface, and form part of the claimed design.

The outer broken lines showing of the display screen or portion thereof are for the purpose of illustrating environmental structure and form no part of the claimed design. The even dash broken lines showing portions of the graphical user interface are for the purpose of illustrating environmental structure and form no part of the claimed design.

The appearance of the image sequentially transitions between the images shown in FIGS. 1-5 , FIGS. 6-10 , and FIGS. 11-15 . The process or period in which one image transitions to another forms no part of the claimed design.