Hi Emme,
Sorry to have no answer for you, but there is no native given way to my knowledge.
A material can be even applied from a higher hierarchy object and it can be animated over time even, or as the most right sided material has the option to cover all the ones more left sided, this could be a long list. If that list couldn’t be long, then the question might be not given at all perhaps. Either way, I’m not aware of a solution for that, but if needed, perhaps one of the Python wizards might has an idea.
Materials and where they applied to are cataloged in the Assigns are of the Material, but not in the other direction.
All the best
