Mirroring a hierarchy of sprites

I'm trying to make a giant boss character that jumps and changes direction depending on whether the player is left or right of it. But for something that should be as simple as just mirroring everything, I've never found a straightforward answer on how to do this, even if I redo all of the animations and rearrange the sprites by scratch. At this point, I tried nearly everything and I'm just asking because I'm out of ideas.

If you want me to post more pictures or the file, I'll do so.

As you can tell, everything is very basic, but I just wanted to alpha-test the mechanics before putting more effort into the sprites. There are a lot of other mechanics I want to have, but I just want to get the most important things done first.

if the hierarchy children have width height checked, mirroring the parent should work with the children

Thank you, that solves how to do it within game. But if I wanted to test the animations and mechanics in the layout editor, is there an easier way to mirror? Oherwise it comes out looking like the first pic.