You probably forgot to mark package as dirty and notify asset registry that it has been created.
if ( Asset != NewStaticMesh )
{
FAssetRegistryModule::AssetCreated(Asset);
Asset->MarkPackageDirty();
}
}
The package creation follows same route everywhere (can be tempalted), and the part where you mark package as dirty AFTER you’ve created actual asset is easy to miss.
The part of fbx importer where it creates materials is easier to follow than static mesh, so you could look there for package creation part.
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Also, please consider adding wiki article or just a post somewhere once you’ve figured out static meshes. few sentences with mentions of relevant apis/methods/fields would be enough.