Display Screen or Portion Thereof of a Device with Transitional Graphical User Interface

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

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

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

FIG. 4 is a front view of a fourth image thereof; and,

FIG. 5 is a front view of a fifth image thereof.

The broken line showing of the display screen or portion thereof in all views forms no part of the claimed design.

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