Currently, the content browser is static and just mirrors the ‘User Content’ folder.
All assets you want to use to build scenes should be placed here.
Thumbnails for assets should be located in the "Thumbnails" folder that fully mirrors the User Content folder hierarchy, excluding textures.
You can generate thumbnails using the generator or create them manually. Textures are processed automatically. Thumbnails should have the same name as their assets.
To automatically generate the required thumbnails, open the StaticThumbnailsMap.
If you select BP_EditorThumbnailBuilder, you have two options:
Often, the editor doesn't pick up the textures of captured materials on the first pass. In this case, you should repeat the operation.