Display Screen or Portion Thereof with Transitional Graphical User Interface

FIG. 1 is a front view of an electronic device having a display screen or portion thereof with transitional graphical user interface showing a first image of a first embodiment of our new design;

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 front view of an electronic device having a display screen or portion thereof with transitional graphical user interface showing a first image of a second embodiment of our new design;

FIG. 7 is a second image thereof;

FIG. 8 is a third image thereof;

FIG. 9 is a fourth image thereof; and,

FIG. 10 is a fifth image thereof.

The evenly spaced broken lines in the drawings show an electronic device, a display screen or portion thereof with graphical user interface elements that form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 - 5 and 6 - 10 . The process or period in which one image transitions to another image forms no part of the claimed design.