Currently, after importing a more complex 3D model that has a large number of materials, there is no easy way to edit these materials in D5. Let alone apply your own.
Sometimes some elements of the model are inside (although they are visible through transparent elements), or are not so easily accessible
A great solution would be that after selecting this model in D5, a list of all the materials used in this model appeared somewhere on some panel. So that you could select a given material from this list and then edit it normally in the D5 panel on the right (Inspector).
Best Regards
Tomasz