The ornamental design for a tray for holdingartisttools, as shown and described.
FIG. 1 is a front perspective view of a tray for holding artist tools, showing my new design.
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 broken lines showing paint brushes, paint tubes, round paint containers, and a trowel illustrate environmental structure that forms no part of the claimed design.