### 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
Ref<StyleBoxLine> style(memnew(StyleBoxLine));
	style->set_color(p_color);
	style->set_grow_begin(p_grow_begin);
	style->set_grow_end(p_grow_end);
	style->set_thickness(p_thickness);
	style->set_vertical(p_vertical);
	return style;
}
static Ref<ImageTexture> editor_generate_icon(int p_index, float p_scale, float p_saturation, const HashMap<Color, Color> &p_convert_colors = HashMap<Color, Color>()) {
	Ref<Image> img = memnew(Image);
#ifdef MODULE_SVG_ENABLED
	
	
	
	const bool upsample = !Math::is_equal_approx(Math::round(p_scale), p_scale);
	Error err = ImageLoaderSVG::create_image_from_string(img, editor_icons_sources[p_index], p_scale, upsample, p_convert_colors);
	ERR_FAIL_COND_V_MSG(err != OK, Ref<ImageTexture>(), "Failed generating icon, unsupported or invalid SVG data in editor theme.");
	if (p_saturation != 1.0) {
		img->adjust_bcs(1.0, 1.0, p_saturation);
	}
#else
	
	
	img = Image::create_empty(16 * p_scale, 16 * p_scale, false, Image::FORMAT_RGBA8);
#endif
	return ImageTexture::create_from_image(img);
}
float get_gizmo_handle_scale(const String &gizmo_handle_name = "") {