To remove an asset
The selected asset node is removed from the graph area of the Hypergraph and deleted from the file. The nodes within the deleted asset are either moved to the parent asset (if one exists), or to the top level of the dependency graph. Note that all connections (published or unpublished) to and from the internal nodes of the asset are retained.
You cannot removed locked assets from a scene.
To remove all the assets in your scene
All the assets in the scene are removed, but their contents remain in the scene.