If a fmx::Data contains an external container, we can cast it to text and get paths from that text.
As FileMaker has a lot of prefixes, can have relative paths to database, it would help plugin developers to query the native path of the external file.
inline errcode GetNativePath ( Text &path );
This would return native full qualified path, e.g. "/Users/cs/Documents/Data/test.jpg".
Or an error code if Data is not an external container.
You probably have something similar internally, so exposing it is hopefully not much work.