_createEditorWindow (rootDirectory = null, fileList = [], markdownList = [], options = {}) {
    const editor = new EditorWindow(this._accessor)
    editor.createWindow(rootDirectory, fileList, markdownList, options)
    this._windowManager.add(editor)
    if (this._windowManager.windowCount === 1) {
      this._accessor.menu.setActiveWindow(editor.id)
    }
    return editor
  }
Creates a new editor window.

@param {string} [rootDirectory] The root directory to open.
@param {string[]} [fileList] A list of markdown files to open.
@param {string[]} [markdownList] Array of markdown data to open.
@param {*} [options] The BrowserWindow options.
@returns {EditorWindow} The created editor window.