Display screen or portion thereof with transitional graphical user interface

FIG. 1 is a front view of the first image of a display screen or portion thereof with transitional graphical user interface showing 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 an eighth image thereof;

FIG. 9 is a ninth image thereof;

FIG. 10 is a tenth image thereof;

FIG. 11 is an eleventh image thereof;

FIG. 12 is a front view of the first image in a second embodiment of the display screen or portion thereof with transitional graphical user interface;

FIG. 13 is a second image thereof;

FIG. 14 is a third image thereof;

FIG. 15 is a fourth image thereof;

FIG. 16 is a fifth image thereof;

FIG. 17 is a sixth image thereof;

FIG. 18 is a seventh image thereof;

FIG. 19 is an eighth image thereof;

FIG. 20 is a ninth image thereof;

FIG. 21 is a tenth-image thereof; and,

FIG. 22 is an eleventh image thereof.

The appearance of the transitional graphical user interface sequentially transitions between the images shown in FIGS. 1-11 and between the images shown in FIGS. 12-22 . The process or period in which one image transitions to another in each sequence forms no part of the claimed design.

The broken lines in the figures depict environmental subject matter and form no part of the claimed design. The broken line showing of the display screen is for environmental purposes only and forms no part of the claimed design.