The ornamental design for a tiltrod for a control system for window covering, as shown and described.
FIG. 1 is a perspective view of a tilt rod for a control system for window covering;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The tilt rod for a control system for window covering is shown broken-away in FIGS. 1, 4, 5, 6, and 7 to indicate that a specific length forms no part of the claimed design.