When I want to copy multiple files to the USB stick, I browse the folders, and drag-and-drop it into the USB device. But if I do it multiple times, all copy operations are carried out in parallel, which is suboptimal if all the copy operations are from the same device or targeting the same device. This is feature request I miss in many file managers: it would be nice that at most one copy operation would be carried for each block device involved, so if I have stacked many copies from HD1 to USB1, they would be carried in serial. But if I have stacked another from USB2 to HD2, that one should be carried in parallel (as currently done).
Sorry for the very late reply ! Thunar was lacking a maintainer for long time. There is already a Bug for that; Bug #16688 If you can, please take a try for the attached patch (I still have to review/test it myself) Not sure yet if serialization only is done for block devices using that patch *** This bug has been marked as a duplicate of bug 16688 ***