createMetaFile = (logger) => {

  if (utils.tiddlerExists(env.ref.sysMeta)) {
    return;
  }

  logger('warn', 'Creating meta file');

  const plugin = $tw.wiki.getTiddler(env.path.pluginRoot);

  $tw.wiki.setTiddlerData(env.ref.sysMeta, {
    // the version originally installed
    originalVersion: plugin.fields.version,
    // the data structure in use corresponds to version x
    // if the structure is obsolete, it will be automatically
    // fixed by the fixer module.
    dataStructureState: '0.6.9',
    // whether or not to display a welcome message
    showWelcomeMessage: true
  });

}
The meta file keeps track of installation data.