Only if they are downloaded from DLS or modified. If they are base, built-in, packaged, or payware, they cannot be individually deleted. Before deleting any assets, you may want to right-click them and select "Show dependents", to see if any routes or other assets have them as a dependency, although if an asset is showing as "obsolete", it means you already have the newer version. You can verify by right-clicking and selecting "List Asset Versions".
