Blender 2.80 UILayout expandable sub column/box

How do you make a expandable sub column/box? (Like “Delta Transform” in Object tab > Transform or “Advanced” in Render tab > Sampling)

This is a stupid question, but I can not find it.

I think this may answer your question:

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It does. Thank you!

I thought it would be just layout like box() or row().
As far as I can see, the sub panel class can only be attached to the bottom of an other panel class.

The solution (correct me, if I’m wrong):
Create a panel class and set bl_parent_id to bl_idname of the other panel class you want to attach the sub panel to.