Display Screen or Portion Thereof with a Transitional Graphical User Interface

FIG. 1 is a first embodiment showing a first image of a display screen or portion thereof with a transitional graphical user interface;

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; and

FIG. 7 is a seventh image thereof.

FIG. 8 is a second embodiment showing a first image of a display screen or portion thereof with a transitional graphical user interface;

FIG. 9 is a second image thereof;

FIG. 10 is a third image thereof;

FIG. 11 is a fourth image thereof;

FIG. 12 is a fifth image thereof; and,

FIG. 13 is a sixth image thereof.

The outermost set of broken lines in FIGS. 1 and 8 illustrate an electronic device and form no part of the claimed design. The dot-dash lines immediately adjacent the transitional graphical user interface in FIGS. 1 - 13 illustrate the display screen or portion thereof and form no part of the claimed design.

The appearance of the graphical user interface sequentially transitions between the images shown in FIGS. 1 - 7 in embodiment 1, and Figures 8 - 13 in embodiment 2. The process or period in which one image transitions to another forms no part of the claimed design.