Shape Key Collections is an add-on that introduces a folder management system for shape keys in Blender. It allows users to structure their shape keys into a hierarchy of folders and subfolders, keeping the interface organized when working with complex meshes. Users can move keys up and down within folders, duplicate entire folders, and manage visibility by opening or closing folder groups. It also includes a Split Keys feature, which groups up to three related shape keys together to display their values in a single location. Additionally, a tracking system ensures that modifiers applied as shape keys are correctly registered within the folder structure.