Missing Texture Sets

I have been trying to figure out the same thing (i.e., how to import a model with different texture sets since my models do not have the color IDs that would let me use the geometry masking).  Based on some experimenting and the note from Jeremie I figured out a way that works for me:

1 - split the model into different subtools in ZBrushCORE.

2- Use the 3D Print ZPlugin to export an OBJ file with all the subtools in one file. (Note: to the best of my knowledge color information cannot be exported from the CORE version.)

3 - Import that OBJ into Stager.

4 - Add a material to each part of the model.

5 - Export that as a GLTF file.  (I cannot get this to work using an OBJ file; Painter will not import the the model at all.)

6- Open the GLTF with Painter.  I get a texture set for each part that came out of ZBrushCORE wether or  not the materials applied in Stager  are the same or different.  This also appear to be the case when I open the MeetMat sample.

Marmoset Toolbag3 will also open the OBJ from ZBrushCORE with multiple parts that can be individually textured.

I am very new to the Adobe 3D space and texturing in general so take this with a grain of salt.

A question:  Is it possible to separate a model into parts that can be textured separatly from within Substance Painter ?