Simulate a Drop, Motion Path, Drag and Drop, Motion Path end in Drop Target

As you said, you cannot take advantage of the drop target's functionality unless your learner actually clicks and drags the item.

If you absolutely must have the functionality you describe, it can be done, if you have the ability and willingness to invest adequate resources.

What it requires is to place each drop item in a possible ending position on the drop target. When it is there, add a motion path to it (I prefer a line), and set its length to 0. When the first motion path ends, move the item on the second path. That will cause it instantly to jump to that position on the screen. Then all you have to do is create a similar path that moves it to every possible place you want it to end, and create the same paths for all the other items. Add a variable to keep track of how many items have been chosen, and use that for the condition of triggers that move (for example,) Item 1 on Path 4 if variable WhichMove = 3 (This is the third item moved).

Not complicated, but a lot of work.