Thanks for the reply, as I said not sure if it is new, but it is for sure a bug, files should be deleted from the Temp folder once the drag and drop done.

I don't use this feature, in fact it was a coincidence that I transferred a big file and noticed it, otherwise I will not notice it. But there were no other files in the Temp folder, it could be cause Microsoft started cleaning the temp folder in recent releases from Windows. so no need to clean the temp folder.