This simple addon checks each selected mesh and removes unused material slots that could have been still attached to your meshes. I found it pretty useful in cases were you have to separate an imported fbx into different pieces.
By default all the newly created meshes will inherit all the applied materials of the original fbx, even if the single mesh does not use all of them. With MatSlotCleaner, instead of having to go through each mesh and remove unused slots, you can do it with just one click.
Keep in mind that this addon is not deleting unused materials from your blend file (you can easily already do that in default Blender), but it's cleaning the material slots instead.
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