Display screen or portion thereof with transitional graphical user interface

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

FIG. 2 is a second image thereof;

FIG. 3 is a third image thereof;

FIG. 4 is a fourth image thereof; and,

FIG. 5 is a fifth image thereof.

The dot-dash broken lines in the drawings show a display screen or portion thereof and form no part of the claimed design. The remaining broken lines in the drawings, including evenly spaced broken lines and all lined-through text, show the display screen or portion thereof, or an electronic device having a display screen or portion thereof and form no part of the claimed design. The shading of the text depicts contrast in appearance and is part of the claimed design.

The Lorem Ipsum text shown in solid lines is exemplary of typographical content and forms part of the claimed design, but the particular text (e.g., individual letters, sequence of letters, and font) forms no part of the claimed design. Other text and/or content is contemplated by the inventors. The Lorem Ipsum text shown in broken lines forms no part of the claimed design.

The appearance of the transitional images sequentially transitions between the views of FIGS. 1 - 5 . The process or period in which an image transitions to another forms no part of the claimed design.