create-plugincommand will create a Grails plug-in project.
grails create-plugin simple
DescriptionCreates a Grails plug-in project. A Grails plug-in project is just like a regular Grails project except it contains a plug-in descriptor and can be packaged up as a plug-in and installed into other applications.Plug-ins are not just useful for plug-in developers, but also as a way to modularize large Grails applications. Refer to the section on Plug-in Development in the user guide for more information on developing plug-ins for Grails.Usage:
grails create-plugin [name]
StatusFinal- When the plug-in has been created