You can use the Hole Callout tool to create callouts for Hole Wizard slots.
The callout format definition file, install_dir\SolidWorks Corp\SolidWorks\lang\language\calloutformat.txt, has been modified to contain new callouts for each slot combination. New sections have been added for countersunk, plain, and counterbore slots.
The slot callouts are at the end of each standard so you can more easily find them if you want to modify them, or combine them with an already modified calloutformat.txt file.
You can re-attach the callout leader to the slot at any point along the arc sections of the slot. The leader always points to the center of the arc. You can control the angle using the Radial/Diameter leader snap angle. Click to access this option.
The callout displays all slot-related dimensions that are marked for drawing, plus the THRU-ALL note or depth symbol value if the slot is through or blind.
The slot length is determined by the tangent to tangent length of the main part of the slot, not the counterbore or countersink tangents.