Accessing embedded MIDI files via FileSystem API

[ally]

I have a viewport filled with dynamically populated child panels. When one is selected, I have another nested child panel that I'm essentially trying to turn into the MIDI Overlay Floating Tile that lets you drag a MIDI file out into your DAW.

The problem I'm running into is that I can't figure out how to access the embedded MIDI files via the FileSystem API so that I can use them with startExternalFileDrag. I'm loading the files into the MIDI player as a string like this:

MIDIPlayer.setFile("{PROJECT_FOLDER}"+currentMidiFile+".mid", true, true);

But using the {PROJECT_FOLDER} wildcard to try to get an actual file object doesn't appear to work. I guess I could ship the MIDI files in the app data folder, but I feel like I might just be overlooking something here... Is it possible to get a file object for an embedded MIDI file?