PlayIt Software Support

This was answered 5 years ago but wondering if there have been any updates to the now playing plugin since then to allow additional metadata options.  I can only find info in the forums indicating that the below macros are available, however i have stumbled on more that are not documented or I cant find docs on like {{isrc}} and {{guid}}...are there more?

{{artist}}

{{title}}

{{comments}}

{{album}}

{{genre}}

{{year}}

Could  I use  {{filename}} too?

If I could add to the discussion, I need to include 2 fields not in the above list, song duration, and timestamp (the time the song began playing in 24-hour format). This is going out as an HTTP POST to an external URL. The text file being generated will still be the simple {{artist}} - {{title}}. Can those fields be made available if they're not already?