From FDT Documentation
FDT 5.5 introduces a new way of customizing your coding experience with SWFBridge. This is a plugin system which enables you to extend FDT in various ways - including Quick Fixes, custom views and code generation tools.
Note: This feature is still in beta and is subject to change. The best way to get involved in learning how to create and use plugins, check out the SWFBridge mailing list.