https://www.liberkey.com/forum/
If you copy your files to another pc's hard disk then you need to securely delete the copied LiberKey only if you don't want to leave any trace which could be recoverable. Otherwise you can simply delete and empty recycle bin since there will be no other trace.
The "recent" folder is not filled by Liberkey but by Windows itself and list the last opened files, this in not considered by nobody (including any other portable suites) as a "trace".