macOS cannot initialize %_counter% or %_max_counter% inside Actions

[ohrenkino]

Please note that the real reference to these variables would be
%_counter%
and
%_max_counter%
no backslash in the names.
See also the Mac documentation:

Format Strings and Available Placeholders

Mp3tag uses format strings in various of its features to describe the structure of file names and imported data. A format string is built of either standard text (e.g., Music), placeholders (such as %artist%, %title%, ...), or slash characters / that usually denote directory structures. Characters with Special Functionality Some characters have special functionality and need to be treated with extra care. If you experience some unexpected behavior when using format string, check if some of t…