The ornamental design for a heightadjustablestandingdesk, as shown and described.
FIG. 1 is a perspective view of a height adjustable standing desk, showing our new design;
FIG. 2 is a front view of the height adjustable standing desk of FIG. 1;
FIG. 3 is a rear view of the height adjustable standing desk of FIG. 1;
FIG. 4 is a left-side view of the height adjustable standing desk of FIG. 1;
FIG. 5 is a right-side view of the height adjustable standing desk of FIG. 1;
FIG. 6 is a top view of the height adjustable standing desk of FIG. 1;
FIG. 7 is a bottom view of the height adjustable standing desk of FIG. 1; and,
FIG. 8 is an additional perspective view of the height adjustable standing desk of FIG. 1.
The dashed lines showing portions of the height adjustable standing desk are included for the purpose of illustrating environment and form no part of the claimed design.