Vincent Gault shows you can create ID maps directly in Substance 3D Painter with this workflow.

ID maps become helpful when you don’t have any other way to isolate parts of the model in Substance 3D Painter. Vincent GAULT (CGVINNY), a Senior Technical Evangelist at Adobe Substance 3D, shows you can create ID maps directly in 3D Painter using a simple process.

Typically ID Maps are created on the model level before you take and bake them in Painter, but here Vincent shows that you can easily make them in Painter.