SystemTrader allows you to download at once all the sub-folders and stock tickers contained in any source folder (except for data-sources themselves, which contain too much data to be downloaded at once).
In the sidebar, select the folder you want to download in whole1).
Choose Tickers > Download whole folder.
Depending on your connection and the size of the folder, the download may take from a few seconds to several hours. You can stop it at anytime with the Cancel button. Since downloading sub-folders is a lot slower than downloading stock tickers, the pace of the download accelerates substantially once all the folders are downloaded2).