Hi Naoko,
We are in the process of moving SDL TMS to allow translators and reviewers to use the new browser-based editor rather than downloading documents. New functionality for these personas will allow the user to simply move to the next document in their inbox when they are finished working on the current document. This means that there is no requirement to download documents or to open multiple documents for translation/review. I hope this achieves the same goal. Watch out for this functionality coming to SDL TMS in 2018.
David