Undefined Software can be huge. Is there a way to manage it?
Undefined Software is exactly that. It's software that is found on systems during Inventory Scans (File Details mostly) that is not Unmanaged or Managed Software. While you can move Undefined Software to Unmanaged software, there's little reason to do so as that clutters the Unmanaged Software. You can delete them all if you want to, but they will come back with the next Full Inventory scan from your environment. So there is little benefit to doing this.