The ornamental design for the expandable sidelight window curtain rod, as shown and described.
FIG. 1 is a perspective view of an expandable sidelight window curtain rod
showing my new, original and ornamental design;
FIG. 2 is a front elevational view of the expandable sidelight window
curtain rod, the rear elevational view being the same as the front
elevational view; and,
FIG. 3 is a side elevation view thereof with the opposite side being a
mirror image.