Add a paint layer on top of your stack of normal layers, set its blendmode to passthrough. Add an anchor point to that, and use that inside whatever generators you're using.
Use what? Sorry I am not sure I get it . I usually use curvature and world normals for mask generation . They are not represented in the layer stack usually. You mean I have to make a special "curvature" channel and use sbsars to modify it with each new layer ?
I use Painter not very often and accustomed to regularly re-bake curvature and world normals again and again with each new layer added. Vs Designer where you always can produce whatever mask you need at any stage within a sort of combined curvature producing parallel node flow doing it for for any stage . Constantly…