Hi,
for glass and metal material you could make it visible by adding a color texture in the diffuse channel but keeping the diffuse level at 0%. It will not affect the material, but you will not be able to add anything else in the diffuse channel. Also for glass make sure that reflection/refraction is white/100%.
Just another workaround, would be nice too see this actually taken care of by the corona team. Maybe it is already fixed in the newer cinema versions?
Build timestamp: Aug 3 2021 16:40:22
Version: 7.0
Cinema version: R21.207 Cinema 4D (mutli-license)
Cheers,
Ararat