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After installing the plug-in, you are now able to build org.lcsim from within Eclipse.
Building a new project
If you now create a new project, have it depend on the lcsim project in Eclipse. In the properties of the lcsim project, in the build path settings, export the dependencies of the lcsim project, so that they are automatically passed down to the new dependent project. Then code completion should also work in the new project that you just created.