Display Screen or Portion Thereof with a Transitional Graphical User Interface

FIG. 1 is a front view of a display screen or portion thereof with a transitional graphical user interface showing a first image in a sequence according to the new design;

FIG. 2 is a front view of a display screen or portion thereof with a transitional graphical user interface showing a second image in the sequence according to the new design;

FIG. 3 is a front view of a display screen or portion thereof with a transitional graphical user interface showing a third image in the sequence according to the new design;

FIG. 4 is a front view of a display screen or portion thereof with a transitional graphical user interface showing a fourth image in the sequence according to the new design; and,

FIG. 5 is a front view of a display screen or portion thereof with a transitional graphical user interface showing a fifth image in the sequence according to the new design.

The outermost rectangular broken line in the figures illustrates a display screen or portion thereof and forms no part of the claimed design. The remaining broken lines represent elements of the graphical user interface that form no part of the claimed design.

The appearance of the image transitions sequentially between the images shown in FIGS. 1 - 5 . The process or period in which an image transitions to another forms no part of the claimed design.