Display Screen or Portion Thereof with Transitional Graphical User Interface

FIG. 1 is a front view of a first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing 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 sixth image thereof;

FIG. 7 is a seventh image thereof.

FIG. 8 is an eighth image thereof; and,

FIG. 9 is a ninth image thereof.

The outer perimeter illustrated by a pair of dashed broken lines in the drawings illustrates a display screen or portion thereof and forms no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 - 9 . The process or period in which one image transitions to another images forms no part of the claimed design.

The stipple shading in the figures illustrates a contrast of appearance and forms part of the claimed design.