The ornamental design for a displayscreen or portion thereof with transitional icon, as shown and described.
FIG. 1 is a front view of a first image in a sequence according to our design for a display screen or portion thereof with transitional icon;
FIG. 2 is a front view of a second image in the sequence thereof; and,
FIG. 3 is a front view of a third image in the sequence thereof.
The appearance of the claimed design transitions between the images shown in FIGS. 1 through 3. The process or period in which one image transitions to another forms no part of the claimed design.
The broken lines in the drawings are for the purpose of illustrating a display screen or portion thereof and form no part of the claimed design.