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 of the display screen or portion thereof with transitional graphical user interface according to the claimed design;
FIG. 2 is a front view of a second image of the sequence according to the claimed design; and,
FIG. 3 is a front view of a third image of the sequence according to the claimed design.
The gradient background of the graphical user interface is claimed subject matter.
The longer length broken line showing of a display screen and the intermediate length broken line showing of a display screen boundary, are included for the purpose of illustrating environmental structure. The remaining broken lines represent elements of the graphical user interface that are excluded from the claim.
The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-3. The process or period in which one image transitions to another forms no part of the claimed design.