Is There a Way to Script Adding Favorite Actions?

You should look at @DanThomas' famous and elegant KMFAM macro.

Dan's macro is absolutely superb and eminently useful.

My macro methodology is excellent for creating macros and/or actions on the fly with custom features.

You can use a variation of my method to work with your own favorites group by creating macros in a group with one or more actions and then using AppleScript to read them and insert them and change their attributes if desired.

Keyboard Maestro is remarkably flexible.

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