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;

FIG. 2 is the second image thereof; and,

FIG. 3 is the third image thereof.

The dashed broken lines at the periphery of the graphical user interface illustrates the display screen, and the remaining broken lines illustrate portions of the transitional graphical user interface. None of the broken lines form part of the claimed design.

The appearance of the graphical user interface sequentially transitions between the images shown in FIGS. 1 - 3 .

The process or period in which one image transitions to another image forms no part of the claimed design.