Display Screen or Portion Thereof with Transitional Graphical User Interface

FIG. 1 is a first image in a sequence 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; and,

FIG. 12 is a twelfth image thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 - 12 . This process or period forms no part of the claimed design. The long and short dashed broken line showing of a mobile terminal in FIGS. 1 - 12 forms no part of the claimed design. The mobile terminal, display screen, and the text, numbers, symbols and images of the graphical user interface shown in broken line in FIGS. 1 - 12 depict subject matter that forms no part of the claimed design.