Display Panel or Portion Thereof with Graphical User Interface

FIG. 1 is a front view of a display panel or portion thereof with graphical user interface according to a first embodiment of our new design; and,

FIG. 2 is another front view thereof shown with the addition of environmental subject matter.

The broken line outline of a mobile device in FIG. 2 depicts environmental structure of a display panel or portion thereof and forms no part of the claimed design. The dot-dash broken lines in the drawings represent boundaries of the claimed design and form no part of the claimed design. All other broken lines in the drawings depict portions of a graphical user interface that form no part of the claimed design.