If you look at your userlib in the project, you should see both the library (e.g. with a name like "commons-codec-1.15.jar") and a "requiredlib" file, like "commons-codec-1.15.jar.ExcelImporter.RequiredLib". These files should show you which module uses a library (in this case, the ExcelImporter). Do make sure you test properly after updating or removing a library.