Backup and restore tags to/from .fpl files

Add all files to playlist.

Make sure tag data is as you want it.

Save playlist in fpl format.

Do whatever to the files that will destroy the tags.

Add all files to playlist.

Select all files, go Database > Remove files from database.

Clear playlist, close Foobar2000 and restart it.

Load fpl file.

Go Database > rewrite tags.