You can drag files etc. onto taskbar icons and it will bring that window to the foreground for you to choose where to drop it. What else do you expect dragging things onto the taskbar icons to do?
not OP, but in macOS, you can drag a file onto a dock icon and that program will open the file if possible. very handy - i use it with Xld, an audio transcoding app. it runs quietly in the background and whenever i need to convert a bunch of FLACs to MP3 (or whatever) i can just drag the folder to the icon and 10 seconds later everything is good to go, without ever really directly interacting with Xld.
not OP, but in macOS, you can drag a file onto a dock icon and that program will open the file if possible. very handy - i use it with Xld, an audio transcoding app. it runs quietly in the background and whenever i need to convert a bunch of FLACs to MP3 (or whatever) i can just drag the folder to the icon and 10 seconds later everything is good to go, without ever really directly interacting with Xld.