Answering my own question:
https://kotlinlang.slack.com/archives/CJLTWPH7S/p1601966418067900 I have created a working example of how to drag&drop in compose. See
https://github.com/jcraane/JetpackComposeDragAndDrop
For the view that can be dropped as well as the drop targets I use the onPositioned and store the global bounds in variables. When the component is dropped, I check if the rect of the dropped view intersects with the bounds of the drop targets.
Although this is a working example I am not sure this is the correct way. Also the mapping between the rects and the drop targets must be made more explicit but it is a start.