Display Screen or Portion Thereof with Transitional Graphical User Interface

FIG. 1 is a front view of a first image of a display screen or portion thereof with transitional graphical user interface, illustrating our new design;

FIG. 2 is a front view of a second image thereof;

FIG. 3 is a front view of a third image thereof;

FIG. 4 is a front view of a fourth image thereof;

FIG. 5 is a front view of a fifth image thereof; and,

FIG. 6 is a front view of a sixth image thereof.

The appearance of the graphical user interface transitions between the images shown in FIGS. 1 - 6 . The process, period, or order in which an image transitions to another forms no part of the claimed design.

The broken line rectangle showing the display screen illustrates portions of the display screen or portion thereof with transitional graphical user interface that form no part of the claimed design. The other broken lines illustrates portions of the display screen or portion thereof with transitional graphical user interface that form no part of the claimed design.