The situation: I have a note and like to create some connected »child notes« with »ctrl-cmd-right-arrow«, switching back to the »parent«, »ctrl-cmd-right-arrow« again. All the »child notes« lay on each other, but of course it makes more sense to have them stacked (like menu »Notes -> Stack«) automat...

No. Not note-items should be posted on a connector, but labels!
When I like to insert a note between to existing notes, it has to be connected to the note before and next.

I find a concept of labels very useful. A label, which will be »glued« on the connector without disrupting it.