How to tell if an asset have missing materials?

My content folder is filled with imported third party uassets. Some loaded well, but others didn’t due to wrong references. Nevertheless, the ones that didn’t still have a textured thumbnail, so the only way to tell if it is going to have missing materials or textures is to either use the Reference Viewer, or to load the asset and see if it is going to be covered by the checkerboard pattern. Either way takes time and needs to be done on a single asset at a time.

Is there a way to force UE to update the thumbnails, so that I can see upfront which assets are textured and which aren’t? Any other solution?

If not, is there a way to simultaneously delete an asset and all other content that it uses, such as materials, textures, functions, etc?