Display Screen or Portion Thereof with Transitional Graphical User Interface

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

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 first image in a sequence of a display screen or portion thereof with transitional graphical user interface, showing our new design in a second embodiment;

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

FIG. 6 is a front view of the third image thereof.

FIG. 7 is a front view of the first image in a sequence of a display screen or portion thereof with transitional graphical user interface, showing our new design in a third embodiment;

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

FIG. 9 is a front view of the third image thereof;

FIG. 10 is a front view of the first image in a sequence of a display screen or portion thereof with transitional graphical user interface, showing our new design in a fourth embodiment;

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

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

FIG. 13 is a front view of the first image in a sequence of a display screen or portion thereof with transitional graphical user interface, showing our new design in a fifth embodiment;

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

FIG. 15 is a front view of the third image thereof;

FIG. 16 is a front view of the fourth image thereof;

FIG. 17 is a front view of the fifth image thereof;

FIG. 18 is a front view of the first image in a sequence of a display screen or portion thereof with transitional graphical user interface, showing our new design in a sixth embodiment;

FIG. 19 is a front view of the second image thereof;

FIG. 20 is a front view of the third image thereof;

FIG. 21 is a front view of the fourth image thereof; and,

FIG. 22 is a front view of the fifth image thereof.

The broken lines showing the display screen or portion thereof in FIGS. 1 - 3 , 7 - 9 , 13 - 17 , and an alternate display screen or portion thereof in FIGS. 4 - 6 , 10 - 12 , 18 - 22 form no part of the claimed design. The remaining broken lines show portions of the transitional graphical user interface that form no part of the claimed design.