The ornamental design for a displayscreen or portion thereof with a transitionalgraphicaluserinterface, as shown and described.
FIG. 1 is a front view of a display screen or portion thereof with a transitional graphical user interface showing a first image in a sequence; and,
FIG. 2 is a front view showing a second image in the sequence.
The longer-incremented broken lines show a display screen portion to illustrate environment and form no part of the claimed design. The dash-dot-dash broken lines of certain features define boundaries for those features and form no part of the claimed design. The finer-incremented broken lines in the remainder of the graphical user interface form no part of the claimed design.
The grayscale in the drawings indicates a contrast of appearance.
The subject matter in this patent includes a process or period in which an image changes into another image. The process or period in which an image transitions to another image forms no part of the claimed design.