Hi everyone, if you’re still having this issue, try my plugin “AssetProcessor”.
This is a versatile plugin designed for bulk editing, filtering, and checking assets. You can edit almost any UProperty, including those only modifiable via C++, as long as you know the modification is valid.
Since the material of a mesh is also a UProperty, this plugin can handle it as well. For applying material to many meshes at once, use the rule setup shown below.
Below are the YouTube tutorial video link and FAB link, hope this helps! 
