Opens a sheet that lets you choose a folder to which the selected records will be exported.
Please note that, because the library is open, it is not necessary to export files in order to open them with other applications. You could instead use the Open in External Viewer or Reveal In Finder commands. The Export… command is intended for when you want to make copies of the selected files or when the selected records are scattered throughout the library so that they would not be easy to access from the Finder.