About 3GX plugins
What are .3gx files?
.3GX (3ds Game eXtension) is a plugin file format (evolved from NTR's .plg format) which allows extra C/C++/asm code to be loaded into an application at runtime and then executed.
What can plugins do?
As the file format name suggests, plugins can be used to extend game functionality, from game mods, to trainers or cheat loaders. One example of a plugin is the CTRPluginFramework Blank Plugin.
How can I install plugins?
Plugins can be placed at 2 locations:
sd:/luma/plugins/<TITLEID>/<filename>.3gx
to set a plugin for a specified title (higher priority)sd:/luma/plugins/default.3gx
to set a plugin which would be loaded for all games (lower priority)
Default plugin is only loaded if no specific plugin is found.
How can I make my own plugins?
An api is available to allow you to create your own plugins using a menu easily.
An example is available here.