No editable arrays in 4.20?

So you apparently can’t edit array elements in a level blueprint.

I saw the Developers’ response “Going forward with 4.20 you will only be able to set actor references on an instance of a Blueprint in a level, but not in the class defaults of a Blueprint.” (Unreal Engine Issues and Bug Tracker (UE-60132)).

How do I create an instance of a level blueprint? Or is it not the case?

Do I have to make arrays on BeginPlay, or is there any way around?

I believe there were similar questions, but none of the answers helped me.
Thank you in advance.

This is related to Editing this value in a Class Default Object not allowed? - World Creation - Unreal Engine Forums