You should be able to add the pointer to your array within the Blueprint editor. Do you see the array property in the blueprint? Is it editable but not accepting your component, or is it greyed out?
You’re not going to be able to reference the ADoor actor directly in the Blueprint viewport. In your hierarchy you’re adding a UChildActorComponent, which is not an ADoor actor but rather holds your ADoor actor; so it’s not valid for the array of ADoor pointers.
You’ll need to get a reference to your child actor and call GetChildActor from it, then add the returned pointer to your array. You can do that in the Blueprint construction script, or in the event graph of your blueprint; or you can spawn your UChildActorComponents in your cpp constructor, or do them dynamically during runtime in another method.
OR, you can make your array an array of child actor components: