Display Screen or Portion Thereof with Transitional Graphical User Interface

FIG. 1 is a top view of an image for a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is a perspective view of a first image in a sequence thereof; and,

FIG. 3 is a perspective view of a second image thereof.

The appearance of the transitional images sequentially transition between the images shown in FIGS. 2 through 3 .

The subject matter of this patent includes a process or period in which an image changes into another image. This process or period forms no part of the claimed design.

The outer perimeter broken lines in the drawings represent a display screen or portion thereof and form no part of the claimed design. The remaining broken lines in the drawings illustrate portions of the transitional graphical user interface that form no part of the claimed design.