The current problem is that if the digikam user want to move an album to a different path from the root of the device its currently on, or to a different device, digikam will show the album with a red 'x' indicating that the path does not exist.  The user could delete the album and create another using the new path, however I'm not sure if that has undesired side effects and it will potentially take a long time to scan all the album photos.

This is "easily" fixed (for a knowledgeable user) by updating the database by hand, namely the identifier column and/or specificPath column of the AlbumRoots table needs to be updated.  This should be allowed by the UI so that everyone has a chance to do this.

I suggest having an edit icon button which pops up a file chooser dialog for the user to select the new location of the album.  The FHS path should be all that is needed to figure out the needed column values.