Making child scenes, how?

[fluid bane]

One the left acts like one on the right with editable children

Which one is the preferred way?

[lilac silo]

There's no real preferred way, but the one on the right is more convenient.

The best way to look at it is that the scene is self contained. You can reuse it in multiple levels or multiple different trees and you know it's going to have the same structure

As an example, you could have an enemy as it's own scene then just drag and drop bad guys directly into the scene without setting each one up individually.