Advanced_Morphs_Remove_Unused_Drivers - Diffeomorphic/import_daz GitHub Wiki
Remove Unused Drivers
It can happen that some drivers become corrupt. If we e.g. remove some shapekeys by hand, the corresponding drivers are still there, but the Python expressions has become invalid.

Or if we delete the armature, the mesh shapekeys remain driven by rig properties of the now non-existent rig.

The Remove Unused Drivers cleans things up by deleting all drivers that have become invalid.