There are a couple of ways to account for the weight of a stone veneer on a cantilevered retaining wall:
Option A: You can apply the veneer weight as an axial load by going to Loads > Loads > Axial Load Applied to Top of Stem.
If your design includes seismic considerations, you may also want to add a lateral load for the veneer under Loads > Loads > Applied Lateral Load on Stem. This is important because the option under Loads > Seismic > Seismic due to Stem Self-Weight does not include any applied axial loads—so the stone veneer’s contribution would be missed unless added separately.
Option B: You can apply a wall weight factor in the Stem tab to account for the total weight of the wall, including the stone veneer.
With this option, if your design includes seismic considerations, selecting the checkbox under Loads > Seismic > Seismic due to Stem Self-Weight will include the additional weight of the veneer.