Official comment
If you want to have the music stored on the external drive, then you can follow my video guide - and if you want to use internally stored music, you can still add that to the library (whether the database itself is stored externally or internally).
If the database is external, moving the drive to another computer won't have access to the songs that were stored on the internal drive.
If the database is internal, removing the external drive will remove access to those songs, likewise, moving that drive to another computer won't have your library with it.
All depends what you want to do!