XPLMReloadPlugins
XPLM_API void XPLMReloadPlugins(void);
This routine reloads all plug-ins. Once this routine is called and you return from the callback you were within (e.g. a menu select callback) you will receive your XPluginDisable and XPluginStop callbacks and your DLL will be unloaded, then the start process happens as if the sim was starting up.