First, please confirm that you really did do what the OP you quoted did, which is now referred to as "Relink Music File Paths" and is accessed by File-->Library-->Relink Music File Paths. If so, please confirm that all of your moved files and playlists do PLAY fine from MusicBee after doing this.
If they are all found/play OK in MusicBee, try Tools-->Advanced-->Compress Library, followed by Tools-->Advanced--> Rescan all Files. This is just to cover all bases! It may or may not resolve your problem with being able to edit them, which if it continues could be due to Windows folder permission/rights issues at the new location.