Why would you put " - some text" (the same text?) after all fields at once?
I can't imagine how it make sense to write such a text for title, artist, album, composer and filename.
It's not possible to have one quick action or converter adding "some text" to multiple fields.
However, you can create an action group with one "Format value" action for each field you want to modify (given that you want to apply this more than once).
However, you can create an action group with one "Format value" action for each field you want to modify (given that you want to apply this more than once).