### 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
theme->set_icon("zoom_out", "GraphEdit", theme->get_icon(SNAME("ZoomLess"), SNAME("EditorIcons")));
	theme->set_icon("zoom_in", "GraphEdit", theme->get_icon(SNAME("ZoomMore"), SNAME("EditorIcons")));
	theme->set_icon("zoom_reset", "GraphEdit", theme->get_icon(SNAME("ZoomReset"), SNAME("EditorIcons")));
	theme->set_icon("grid_toggle", "GraphEdit", theme->get_icon(SNAME("GridToggle"), SNAME("EditorIcons")));
	theme->set_icon("minimap_toggle", "GraphEdit", theme->get_icon(SNAME("GridMinimap"), SNAME("EditorIcons")));
	theme->set_icon("snapping_toggle", "GraphEdit", theme->get_icon(SNAME("SnapGrid"), SNAME("EditorIcons")));
	theme->set_icon("layout", "GraphEdit", theme->get_icon(SNAME("GridLayout"), SNAME("EditorIcons")));
	
	Ref<StyleBoxFlat> style_minimap_bg = make_flat_stylebox(dark_color_1, 0, 0, 0, 0);
	style_minimap_bg->set_border_color(dark_color_3);
	style_minimap_bg->set_border_width_all(1);
	theme->set_stylebox("panel", "GraphEditMinimap", style_minimap_bg);
	Ref<StyleBoxFlat> style_minimap_camera;
	Ref<StyleBoxFlat> style_minimap_node;
	if (dark_theme) {
		style_minimap_camera = make_flat_stylebox(Color(0.65, 0.65, 0.65, 0.2), 0, 0, 0, 0);
		style_minimap_camera->set_border_color(Color(0.65, 0.65, 0.65, 0.45));
		style_minimap_node = make_flat_stylebox(Color(1, 1, 1), 0, 0, 0, 0);
	} else {
		style_minimap_camera = make_flat_stylebox(Color(0.38, 0.38, 0.38, 0.2), 0, 0, 0, 0);
		style_minimap_camera->set_border_color(Color(0.38, 0.38, 0.38, 0.45));
		style_minimap_node = make_flat_stylebox(Color(0, 0, 0), 0, 0, 0, 0);
	}
	style_minimap_camera->set_border_width_all(1);
	theme->set_stylebox("camera", "GraphEditMinimap", style_minimap_camera);
	theme->set_stylebox("node", "GraphEditMinimap", style_minimap_node);
	Color minimap_resizer_color;
	if (dark_theme) {
		minimap_resizer_color = Color(1, 1, 1, 0.65);
	} else {