Display Screen or Portion Thereof with Transitional Graphical User Interface

FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing a first image of the claimed 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;

FIG. 9 is a ninth image thereof;

FIG. 10 is a tenth image thereof;

FIG. 11 is an eleventh image thereof;

FIG. 12 is a twelfth image thereof;

FIG. 13 is a thirteenth image thereof;

FIG. 14 is a fourteenth image thereof;

FIG. 15 is a fifteenth image thereof;

FIG. 16 is a sixteenth image thereof;

FIG. 17 is a seventeenth image thereof; and,

FIG. 18 is an eighteenth image thereof.

The broken lines in the figures forming a rectangle show a display screen or portion thereof, and form no part of the claimed design. The broken lines in the figures forming a circle or variation thereof form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 - 18 . The process or period in which one image transitions to another forms no part of the claimed design.