When developing a plugin, you'll most likely want to see any errors your code produces. To turn error reporting on within Typesetter CMS, open your /index.php file and insert the code define('gpdebug',true); so that you have something like the following
<?php define('gpdebug',true); require_once('include/main.php');
Normally, when a Typesetter CMS plugin is installed, the code is copied from the /addons/-plugin- directory to the /data/_addoncode/-plugin- directory. This can create difficulties for plugin developers since changes to the code in /addons/-plugin- won't be seen because the code being executed is in /addons/_addoncode/-plugin-.
To prevent confusion during development, you should install your plugin in developer mode. To do so, click "Develop" in the "Available Addons" dialog. This will take you through the install process for the plugin, but it will create symbolic links for the /addons/_addoncode/-plugin- folder.