The ornamental design for a heightadjustabletoiletstool, as shown and described.
FIG. 1 is a top-front perspective view of a height adjustable toilet stool showing my new design;
FIG. 2 is a bottom-back perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof;
FIG. 7 is a left view thereof;
FIG. 8 is a right view thereof;
FIG. 9 is a top-front perspective exploded view thereof; and,
FIG. 10 is a bottom-back perspective exploded view thereof.
The broken lines showing of orifices and fasteners in FIG. 1-10 are included for the purpose of showing environmental structure and forms no part of the claimed design.