How to copy one field value to another field?
Example how to copy the content of the ARTIST field to the ALBUMARTIST field:
Create a new action in an existing action group or make a new action group.
Action type: Format value
Field: ALBUMARTIST
Format string: %artist%
Note: If you want to copy all possible values of a field (in case you have multiple artist fields), the internal scripting function $meta_sep can be used in the format string, e.g., $meta_sep(artist,\\\\)