4d59c66 created the issue

Currently when performing a segmented download is performed, the segments are placed into subfolder next to the download location. As a result the combination of the segments into the final file uses the same disk as source and destination, which is always slower than when using separate disk.

By exposing in the preferences a separate path where the temp folder for segments is created, the download can be speed up as the resulting combination of segments would read/write from separate disks.

This is related to defect #11833 and #10961