ok, here is what I do:
I have about 8 different objects with a drag and drop behaviour. I want the player not to be able to drag one object over the other, so he can only place the objects in a free space. Furthermore, I don't want the collisions to be exact, but a collision mask in a circle with a given raduis around each object. I can't use a custom collisionmask, because each object has a physic-behaviour that needs the exact collisionmask. Also it would be quite complicated to have 8 collisionevents in each of the 8 objects. So what I did was to create an extra, invisible object in form of a circle which I attached to each of the 8 objects. Of course I could have done 8 collision objects which I put in a container with each of the 8 main objects - but I thought that quite complicated. So I created ONE collision-object for all 8 objects. In its events I programmed, that when it would overlap with one of his kind, it tells that the main object, which changes its filter colour to red and would go back to its initial position when the left mouse button is released. This means, I have to always make sure that the right collision object is exactly on the position of its parent. I solved this by creating the collisionproject at startup, giving him the UID of the parent and, in case of drag and drop, picking the object by comparing the stored parents UID with the UID of the selected object. This works well, but I wonder if there is an easier way.
And no I did not come from MMF, but from gamemaker, where I solved many problems using IDs, that's true. And I have to admit, that I sometimes have difficulties to get used to the construct-style. For example in gamemaker one could use scripts, that you'd execute with passing arguments - for example an object ID. That was very useful, you could use the same piece of code for many different objects, you only had to pass the object ID to the script and it would execute all the code with exactly this object. I don't seem to find a similar possibility in contruct, but maybe I just have to change my way of thinking
Thanks for the reply,
Maenny