Master Shape Keys is a toolset for managing and manipulating shape keys in Blender. It allows users to split existing shape keys into multiple unique keys based on vertex groups, such as splitting a single expression into left and right sides.

The add-on features tools for combining multiple shape keys, allowing them to activate consecutively or additively. A sync function enables a shape key on one object to drive a shape key on another object. It also includes a baking feature to merge keys while preserving animation data, which is useful for exporting to game engines or rendering on farms.

Included in the toolset is a folder-based management system for organizing shape keys into collections and subcollections.