IMO, Mp3tag's syntax tends to be a little too loose and could use some harder rules and more consistency.
Instead of Format string (not scriptable) I prefer to drop the term completely for these dialogs and rather use one of these:
Dano, please indicate which of those terms you propose for each of:
Convert Text file - Tag (format string not scriptable)
Convert Filename - Tag (format string not scriptable)
Convert Tag - Filename (format string scriptable)
Action Format value (format string scriptable)
Convert Text file - Tag (guessing pattern)
Convert Filename - Tag (guessing pattern)
Convert Tag - Filename (format string)
Action Format value (format string)
OK, I see. Looks good to me. Though I woould prefer matching pattern to guessing pattern.
"Pattern Matching" (german: Musterabgleich) is a well known idiom, that describes very good what is going on e. g. when doing "Convert Filename - Tag".
At first there is a pattern do describe, which must match, to give at last the fitting result.
The idiom "Format String" (german: "Zeichenkette formatieren") is derivated from the C programming language, which provides a function "printf", and means:
"replace each format item in a specified string with the text equivalent of a corresponding object's value"
(german: "ersetze jedes Formatelement in einer angegebenen Zeichenkette durch den Text, der dem Wert eines entsprechenden Objekts entspricht.")
A format item can be any tag-field placeholder like "%TITLE%" or a Mp3tag function expression like "$char(7)".
A format item can also be used alone for itself or in combination with other format items, without any string character around or between the format items.
Well, it seems that we are on a good way to close the traps in the "Convert" area of Mp3tag!
I hope so, but also that this goes across the whole app.