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 our new design.

FIG. 2 is a front view of a display screen or portion thereof with a transitional graphical user interface transitioned in sequence from FIG. 1 showing our new design; and,

FIG. 3 is a front view of a display screen or portion thereof with a transitional graphical user interface transitioned in sequence from FIG. 2 showing our new design.

The appearance of the transitional graphical interface sequentially transitions between the images shown in FIGS. 1 , 2 , and 3 . The process or period in which one image transition to another image forms no part of the claimed design.

The outermost broken lines in the Figures show a display screen or portion thereof on a computing device and form no part of the claimed design. The other broken lines shown in the Figures are environment only and show portions of the transitional graphical user interface that form no part of the claimed design.