Display Screen or Portion Thereof with Transitional Graphical User Interface

FIG. 1 is a front view of a first image of a display screen or portion thereof with transitional graphical user interface showing a first image in a sequence according to 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 sixth image thereof;

FIG. 7 is a seventh image thereof;

FIG. 8 is a an eighth image thereof;

FIG. 9 is a ninth image thereof;

FIG. 10 is a tenth image thereof according to a first embodiment;

FIG. 11 is a an eleventh image thereof according to the first embodiment;

FIG. 12 is a tenth image thereof according to a second embodiment; and,

FIG. 13 is a tenth image thereof according to a third embodiment.

The appearance of the transitional image sequentially transitions between the image shown in FIGS. 1 - 11 , FIGS. 1 - 9 and 12 , and FIGS. 1 - 9 and 13 . The process or period in which one image transitions to another image forms no part of the claimed design. The rectangular broken-line perimeter illustrates a display screen or portion thereof and forms no part of the claimed design. The remaining broken lines shown in the drawings illustrate parts of the graphical user interface that form no part of the claimed design.