Haxegon supports a simple plugin system to extend it's functionality. Generally, you install a plugin by copying a single .hx file to your plugins folder. If you do not have a plugins folder, make sure you're using the latest blank haxegon project template.
As of 0.12.0, there are three plugins for Haxegon:
Layers: A simplified display list.
Filters: A fullscreen post-processing shader plugin.
imGui: A simple imgui library.
More plugins will be coming before 1.0!
Are you interested in making a haxegon plugin of your own? Great! Read here for some developer guidelines!
(To do: make a proper plugin page)