Display Screen or Portion Thereof with Transitional Graphical User Interface

The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawings will be provided by the Office upon request and payment of the necessary fee.

FIG. 1 is 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; and,

FIG. 7 is a seventh image thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 to 7 . The process or period in which one image transitions to another image forms no part of the claimed design. The broken line showing the mouse position on the display screen in FIG. 6 forms no part of the claimed design. The outer perimeter shown in dashed broken lines in the figures illustrates a display screen or portion thereof and forms no part of the claimed design.