heya; er... as far as i know, there is no way to add/subtract/change materials in p4. (can the grouping tool do that?) if you change the geometry in p4 (with magnets, or add props or whatever); zero the figure, export as an obj, then copy the cr2 of the base figure and just edit it to point to the new obj. saving the new figure with props to the library will not create a new obj, just a new cr2.