I claim the ornamental design for a vial support assembly for a level, as shown and described.
FIG. 1 is a front, bottom perspective view of our new, original and ornamental design for a vial support assembly, with the broken lines showing a level for illustrative purposes;
FIG. 2 is a front elevational view thereof; and,
FIG. 3 is a rear elevational view thereof.
The broken lines are for illustrative purposes only and form no part of the claimed design.