SongKong Scripter allows us to write Javascript to modify metadata fields to new values. SongKong comes with a number of default scripts that can be used for common tasks or as part of a larger script.
From the Preferences/Scripter tab we can Edit, Add, Clone or Delete these scripts.
Select Edit to modify or simply just view a script.
We can select Add to create a new blank script, but it is usually easier to select another script to base our new script on and then select Clone to create a new script with a name based on the existing script and the script itself copied over from the cloned script.