Display Screen or Portion Thereof with Transitional Graphical User Interface

The file of any patent that grants from the present application contains at least one drawing/photograph executed in color. Copies of any patent that grants from the present application with color drawing(s)/photograph(s) will be provided by the Office upon request and payment of the necessary fee.

FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing our new design; and,

FIG. 2 is a front view of a second image thereof.

The appearance of the image transitions sequentially between the images shown in FIGS. 1 - 2 . The process or period in which one images transitions to another forms no part of the claimed design.

The outermost dot-dash broken lines in FIGS. 1 - 2 show a display screen or portion thereof, and form no part of the claimed design.