Long answer: Possible to mimic. Drag and Drop and define the wrapping div of an iframe as the drop-target (most libraries support that). Once it is dropped you should use your preferred messaging API between the iframes and "inform" the iframe that it should handle the drop event. You can pass strings (and use JSON data if needed) - on the "other side" (inside the iframe) your code should be able to handle the drop.
I'm not sure about how much support you can get if you want to drop into specific portions of the iframe, If I had to do it I would check if it is possible to calculate the x/y position of the drop, then on the "other side" calculate what is positioned there and respond accordingly.
Avichay Eyal
Quick answer: Impossible.
Long answer: Possible to mimic. Drag and Drop and define the wrapping div of an iframe as the drop-target (most libraries support that). Once it is dropped you should use your preferred messaging API between the iframes and "inform" the iframe that it should handle the drop event. You can pass strings (and use JSON data if needed) - on the "other side" (inside the iframe) your code should be able to handle the drop.
I'm not sure about how much support you can get if you want to drop into specific portions of the iframe, If I had to do it I would check if it is possible to calculate the x/y position of the drop, then on the "other side" calculate what is positioned there and respond accordingly.
It's going to be rough, but possible. Good luck.