Display screen or portion thereof with transitional graphical user interface

FIG. 1 is a first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design in accordance to a first embodiment;

FIG. 2 is the second image in a sequence thereof;

FIG. 3 is the third image in a sequence thereof;

FIG. 4 is the fourth image in a sequence thereof;

FIG. 5 is a first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design in accordance to a second embodiment;

FIG. 6 is the second image in a sequence thereof;

FIG. 7 is the third image in a sequence thereof; and,

FIG. 8 is the fourth image in a sequence thereof.

The outermost broken lines illustrate the display screen or portion thereof and form no part of the claimed design. The remaining broken lines in the figures depict portions of the graphical user interface which form no part of the claimed design.

The appearance of the graphical user interface sequentially transitions between the images shown in FIGS. 1 - 4 , in FIGS. 5 - 8 , respectively. The process or period in which one image transitions to another forms no part of the claimed design.