The ornamental design for a displayscreen or portion thereof with transitional graphical user interface, as shown and described.
FIG. 1 is a front view of a first image of a sequence according to the claimed design;
FIG. 2 is a front view of a second image of the sequence according to the claimed design;
FIG. 3 is a front view of a third image of the sequence according to the claimed design; and,
FIG. 4 is a front view of a fourth image of the sequence according to the claimed design.
The longer-length dashed broken lines show an electronic device and form no part of the claimed design. The shorter-length dashed broken lines show the perimeter of a display screen and various elements within the graphical user interface, and form no part of the claimed design. The dot-dash broken line shows a portion of the graphical user interface, and forms no part of the claimed design.
The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-4. The process or period in which one image transitions to another forms no part of the claimed design.