Creating Extensions for Fusion 2.5 & Fusion 2.5 Developer
The extension SDKs (Software Development Kits) allows you to create your very own extensions for Fusion 2.5 and the various export modules. You will need to know a little C++ and the export module language to create an extension.
Download the SDKs you wish to develop with and start developing your very own extensions. These extensions can magnify the power of your Fusion 2.5 applications and games. With the SDKs, you can create your own extensions that work with additional built-in platform functions, communicate with existing, 3rd-Party SDKs and APIs.
Flash SDK: Forum post
If you get an error when going to the links, you are either not logged in to the forums, or you have not registered Fusion or the exporter in the Community Passport. These are all the official Clickteam exporter links.
Add your finished extension to the Extension Manager inside of Fusion 2.5: