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 in a sequence according to a first embodiment; and
FIG. 2 is a front view of a second image in the sequence thereof.
FIG. 3 is a front view of a first image in a sequence according to a second embodiment; and,
FIG. 4 is a front view of a second image in the sequence thereof.
The appearance of the transitional image transitions between the images shown in FIGS. 1-2 and 3-4, respectively. The process or period in which one image transitions to another forms no part of the claimed design.
The long-dash broken lines showing a device, the medium-dash broken line showing the display screen or portion thereof, and all other broken lines showing portions of the graphical user interface, form no part of the claimed design.