I’ve been going over the ConnectionFileDescriptor class trying to figure out the best way to get all this functionality working on Windows. I notice that many fo the connection string types are unused. For example, it seems we never use file://, fd://, tcp-connect://, or accept://

Can I delete these?

Please don't remove anything. The "platform connect" accepts URLs:

(lldb) platform connect file:///dev/s0

So just because we won't see anything in the code doesn't mean it isn't used.