If you want to work with projects or files in your plug-in, there are several useful classes that can help you.
The ProjectUtils class from the org.omnetpp.common plug-in can be used to enumerate open or
referenced projects, or NED folders. You can add OMNeT++ support to existing projects.
If you add org.omnetpp.common to your project dependencies, you can use CDTUtils to enumerate C++
source or excluded folders. MakefileToools and 'MetaMakemake` from org.omnetpp.cdt are used to
control the Makefile generation.
The source of the OMNeT++ plug-ins are bundled with the IDE. You can easily access their documentation.