Thanks for the reply! I am quite new to unreal, so my BP aren’t that high quality yet 
Waht I try to achieve is the following situation:
Here some screenshots of the level:
This is the level as it is build. Static wall with socket (cube) where I want to attach the panel.
The actions I want: overlap green cube with the white (socket) cube → attach the sheet horizontally to the wall. No rotation in any axis.
Cubes are triggers. Socket is in the centre of the white (wall) cube:
So far so good, the panel attach to the white cube socket.
Sheet has grabcomponent and physics enabled.
Then I spawn with a widget another (same) actor and want to attach this above the already placed actor of the panel.
So when green trigger overlaps blue trigger, it must attach to the first panel (so that the green box snaps to the blue box)
And after that it must be possible to remove the attached actor again or even place 2 or 3 more above it in a row.
Also later on, there will be a slection of more BP-actors of different sizes who can be connect to these actors. You can also “delete” a spawned actor by detroy actor.
That’s in short what I want to achieve…