Have you tried to manually rebuild the entire path adding the missing folders after ../Microsoft/ : /Library/Application Support/Microsoft/Office365/User Content.localized/Add-ins.localized/WordRake/ and then copying the file libWordRake.MacOS.Bridge.dylib from the old MacBook ?
If the old file is no longer available maybe a dummy empty file with the same name could trick Office and allow you to delete the Add-in from Word.