Intro to assigning tag fields with scripting on Mac

[ohrenkino]

@greybeard

Assign Beatles to the Title and Yellow Submarine to the Artist

Source format: Beatles - Yellow Submarine
Formatstring: %artist% - %title%

The headline claims something different from the actual example.
The example assigns "Beatles" to ARTIST and "Yellow Submarine" to TITLE.

There are many ways to skin a cat - but I think that the action of the type "Format tag field" is a little easier as you can select the target field from a list of fields.
See also the documentation:

Quick Actions and Action Groups

Mp3tag for Mac provides a variety of Actions, which can be used on filenames and tags. The actions can be applied individually via Actions → Quick Actions ⌥⌘ 6 or be grouped into named and reusable Action Groups via Actions → Actions ⌘ 6. Action Groups serve as repeatable workflows in Mp3tag for Mac. When using Quick Actions you can select one of the different available action types from the list. This action will be applied to the selected files and the changes are saved immediately. Tip 1…

@greybeard

I find it much easier to work in Actions vs. Quick Actions when trying to refine a complicated script

You are right: use the Actions if you want to keep the script definition.
Some actions like "Replace" are one-offs in many cases, so it may not be worthwhile to save the configuration. But that depends on the use-case.