The editor’s built in “delete Assets” window can be a bit misleading
An asset being a “Memory Reference” doesn’t mean it’s used by other assets, it can just mean that it has recently been loaded or is used in the undo system for example. So it’s usually safe to ignore.
Our usual recommendation is to delete your assets after restarting the editor with no level loaded (which usually avoids that)
If an asset shows in the “Asset References” column then that’s a problem, because this would mean the asset is used by another asset.
If that’s the case could you send us a screenshot and how you got to that point?
Thank you!