Display Screen or Portion Thereof with Transitional Icon

FIG. 1 is a front view of a first image in a sequence for a display screen or portion thereof with transitional icon showing our new design;

FIG. 2 is a second image thereof;

FIG. 3 is a third image thereof.

FIG. 4 is a fourth image thereof; and,

FIG. 5 is a fifth image thereof.

The outer perimeter illustrated by a pair of dashed broken lines in the drawings illustrates a display screen or portion thereof and forms no part of the claimed design.

The dot-dash broken lines define the boundaries of the claimed design and form no part thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 - 5 . The process or period in which one image transitions to another images forms no part of the claimed design.