Display Screen or Portion Thereof with Transitional Graphical User Interface

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

FIG. 2 is a front view of a second image in the sequence thereof;

FIG. 3 is a front view of a third image in the sequence thereof;

FIG. 4 is a front view of a fourth image in the sequence thereof;

FIG. 5 is a front view of a fifth image in the sequence thereof;

FIG. 6 is a front view of a sixth image in the sequence thereof;

FIG. 7 is a front view of a seventh image in the sequence thereof; and,

FIG. 8 is a front view of an eighth image in the sequence thereof.

The appearance of the claimed design transitions between the images shown in FIGS. 1 through 8 . The process or period in which one image transitions to another forms no part of the claimed design.

The broken lines in the drawings are for the purpose of illustrating a display screen or portion thereof and portions of the graphical user interface that form no part of the claimed design.