Display screen or portion thereof with transitional graphical user interface

[0001]FIG. 1 is a front view of an electronic device having a display screen or portion thereof with a transitional graphical user interface applied to the display screen or portion thereof and showing a first image of the claimed design;

[0002]FIG. 2 is a second image thereof;

[0003]FIG. 3 is a third image thereof; and,

[0004]FIG. 4 is a fourth image thereof.

[0005]The evenly spaced broken lines in the drawings show the electronic device and the portions of the display screen or portion thereof with transitional graphical user interface, and form no part of the claimed design. The dot-dash broken lines in the drawings show a display screen or portion thereof and form no part of the claimed design.

[0006]The appearance of the transitional image sequentially transitions between the views shown in FIGS. 1-4. The process or period in which an image transitions to another forms no part of the claimed design.