### Godot version

v4.1.1.stable.official [bd6af8e0e]

### System information

Godot v4.1.1.stable - Ubuntu 22.04.2 LTS 22.04 - Vulkan (Forward+) - integrated Intel(R) UHD Graphics 615 (AML-KBL) () - Intel(R) Core(TM) i3-10100Y CPU @ 1.30GHz (4 Threads)

### Issue description

Summary: When editing the subregion of a StyleBoxTexture, it shows me the entire spritesheet of the Atlas texture, instead of the selected portion of the atlas, making it difficult (and non-intuitive) to correctly select the subregion I need. 

What I expect: I understand that the sub-region may be used to emulate the behavior of a nine-patch. So I would expect to see there the subregion that i selected previously from the Atlas as the texture to be shown.

I have only tested this in a Panel Container

### Steps to reproduce

I found this problem when doing these steps:

- Add a PanelContainer node
- In the inspector select Theme Overrrides -> Style -> new StyleBoxTexture
- In the texture of the StyleBoxTexture select new AtlasTexture
- Dropped the spritesheet in the Atlas of the AtlasTexture
- In Region of the AtlasTexture, selected Edit Region and drew the rectangle on the texture i want:
![image](https://github.com/godotengine/godot/assets/1207326/2e9624b1-63bc-4267-8d7f-59e82df7896e)

- Back in the StyleBoxTexture options, in Sub-Region, clicked on Edit Region to select the nine-patch region i need
- Here is where the region editor shows me the entire spritesheet and not the sub-texture i selected from the atlas. The image below shows the axis correctly positioned for the nine-patch to work, but it is not intuitive because it has to be positioned without seeing the correct texture, making it difficult to finetune for some textures.

![image](https://github.com/godotengine/godot/assets/1207326/a5023afd-7e4b-47c8-adfc-03fda7f6301b)


### Minimal reproduction project

N/A
} else {
		style_widget->set_border_color(dark_color_2);
	}
	Ref<StyleBoxFlat> style_widget_disabled = style_widget->duplicate();
	if (draw_extra_borders) {
		style_widget_disabled->set_border_color(extra_border_color_2);
	} else {
		style_widget_disabled->set_border_color(disabled_color);
	}
	style_widget_disabled->set_bg_color(disabled_bg_color);
	Ref<StyleBoxFlat> style_widget_focus = style_widget->duplicate();
	style_widget_focus->set_draw_center(false);
	style_widget_focus->set_border_width_all(Math::round(2 * MAX(1, EDSCALE)));
	style_widget_focus->set_border_color(accent_color);
	Ref<StyleBoxFlat> style_widget_pressed = style_widget->duplicate();
	style_widget_pressed->set_bg_color(dark_color_1.darkened(0.125));
	Ref<StyleBoxFlat> style_widget_hover = style_widget->duplicate();
	style_widget_hover->set_bg_color(mono_color * Color(1, 1, 1, 0.11));
	if (draw_extra_borders) {
		style_widget_hover->set_border_color(extra_border_color_1);
	} else {
		style_widget_hover->set_border_color(mono_color * Color(1, 1, 1, 0.05));
	}
	
	Ref<StyleBoxFlat> style_popup = style_default->duplicate();
	const int popup_margin_size = default_margin_size * EDSCALE * 3;
	style_popup->set_content_margin_all(popup_margin_size);
	style_popup->set_border_color(contrast_color_1);
	const Color shadow_color = Color(0, 0, 0, dark_theme ? 0.3 : 0.1);
	style_popup->set_shadow_color(shadow_color);