The metadatas edited in the file browser are local to Max: they’re not written in the file, but in a database used by Max.
Maybe it is possible to access it using the technique described here.
but I don’t know how the database is called.
It is also possible to save and recall metadata databases using the max messages db.exportmetadata and db.importmetadata. You could try to edit and save these files inside Max.
If you need to change datas like loops, markers, TC, etc. I’m afraid it is not possible. If you want to read markers data, you can use my (still Mac only) sfmarkers~ external.
I wanted to create such an external but I don’t have much time, I didn’t feel there was much interest, and I think a real-time environment may not be the best place to do such thing as saving a big audio file just to add a couple of metadatas takes a lot of time.
"This videoblog demonstrates and explains how custom metadata fields written to audiofiles in a music composition environenment, can be used in combination with OSX spotlight technology (mdfind command basically) to call families of sounds with specific typomorphology."