Blender - Reset all slots material to selected objects with python script
How to delete all unused materials from a Blender 2.8 file, time saving tips for beginners - BlenderNation
GitHub - QCPolmer/Blender-3d-remove-duplicate-materials-in-scene: Run this script from a scene and it will replace all materials with a '.001' or whatever with the material without the number after it. Basically, it is for
MatSlotCleaner - Clean Unused Material Slots With One Click - Blender Market