Questions about custom styles

[SalmonDu]

I made an image using PS to describe my idea. I don't know how to modify the balloon to look like in the image.

The problem I'm having is that, I don't know how to hide the black banner and Button below the DialogueLabel and ResponsesMenu.
I tried to delete them and put DialogueLabel and ResponsesMenu just under a control node, but found that the code would report errors.
Is there any way that I can place DialogueLabel and ResponseMenu freely?

[SalmonDu]

I obtained the method in the Godot document！