You can preview the contents of an asset before you actually create one. This is useful when using the Include Hierarchy option in the Create Advanced Asset Options to confirm you are including the actual hierarchy you want.
To preview the contents of an asset
Any objects that would be placed in the asset are selected in the scene.
Performing a preview operation changes your selection. If you want to preview multiple creation options on the same original selection, you should undo each preview operation before changing options and previewing again.