Display Screen or Portion Thereof with Transitional Graphical User Interface

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

FIG. 7 is a second image thereof;

FIG. 8 is a third image thereof;

FIG. 9 is a fourth image thereof; and,

FIG. 10 is a fifth image thereof.

The outer evenly spaced broken lines illustrate an electronic device, the dot-dash broken lines illustrate the display screen or portion thereof, and the remaining broken lines illustrate portions of the transitional graphical user interface. None of the broken lines forms part of the claimed design.

The appearance of the transitional image sequentially transitions between the views of FIGS. 1 - 5 and FIGS. 6 - 10 . The process or period in which an image transitions to another forms no part of the claimed design.