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 the first image in a sequence of a display screen or portion thereof with transitional graphical user interface, showing our new design;
FIG. 2 is a front view of the second image thereof;
FIG. 3 is a front view of the third image thereof;
FIG. 4 is a front view of the fourth image thereof;
FIG. 5 is a front view of the fifth image thereof;
FIG. 6 is a front view of the sixth image thereof; and,
FIG. 7 is a front view of the seventh image thereof.
The appearance of the transitional graphical user interface sequentially transitions between the images shown in FIGS. 1-7. The process or period in which one image transitions to another forms no part of the claimed design.
The outer perimeter illustrated by a pair of dashed broken lines depicts a display screen or portion thereof and forms no part of the claimed design. The contrast shown in grayscale in the figures depicts a contrast of appearance. The remaining dashed broken lines shown in the figures depict portions of the graphical user interface that form no part of the claimed design.