Adding additional actors to world in editor

I want to be able to add additional actors (of a different class) when dragging a C++ Actor into the world in the editor.

At the moment, when I drag my primary actor class into the world it does nothing. And only once play is hit does it add the actors of the second class. Once you quit the PIE mode, then although the objects of the class are visible in the world outliner, none of their member variables or other things set up in their code exist of course!

Instead, I would like to set up the primary actor so that the first time it is dragged into the world, it creates objects of the secondary class which will all then be available in the editor to modify as well as copied (?) into PIE.

If I override OnConstruction, then the secondary actors can get added to the world there. However, I’m using a TMap to store them and if in the BeginPlay function I log out the TMap.Num() to find how many elements it has, it returns 0 (whereas in the editor the TMap.Num() == 8 which is what I expect).

This is kind of a follow up to my previous question
and I think sounds similar to what this person was asking before too