[plt-scheme] Extensibility of MrEd

Does MrEd contain any hooks for operating-system-specific extensions, 
FFI or otherwise?  What is the best way to access OS-specific UI 
functionality (e.g. system-defined GUI widgets, handling system-specific 
user interaction messages, etc.) in a MrEd program?

I am building an experimental application on a yet-unreleased version of 
a Microsoft OS on yet-unreleased hardware.  And I am hoping not to have 
to roll a homebrew GUI wrapper framework (fraught with danger and sundry 
system event trampolines), or to fork the MrEd DLL source.  What are my 
options?

Thanks,
Ben