You have two options.
1. Requires recompiling:
- If you go into the DesktopModel.as class and in the constructor comment out the listener which listens for the ToastEvent(s). If you're going this far you might want to remove the ToastLoggingTarget on the Desktop.mxml.
2. Modify the javascript, by commenting out the following lines:
- file: js/workspace-init.js
modify the line createToastDiv(); to //createToastDiv(); (just comment it out)
- remove the file js/workspace-toast.js from the js folder.
Try those two options.