### 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_color("close_color", "GraphNode", node_decoration_color);
	theme->set_color("resizer_color", "GraphNode", node_decoration_color);
	theme->set_constant("port_offset", "GraphNode", 0);
	theme->set_constant("title_h_offset", "GraphNode", 12 * EDSCALE);
	theme->set_constant("title_offset", "GraphNode", 21 * EDSCALE);
	theme->set_constant("close_h_offset", "GraphNode", -2 * EDSCALE);
	theme->set_constant("close_offset", "GraphNode", 20 * EDSCALE);
	theme->set_constant("separation", "GraphNode", 1 * EDSCALE);
	theme->set_icon("close", "GraphNode", theme->get_icon(SNAME("GuiCloseCustomizable"), SNAME("EditorIcons")));
	theme->set_icon("resizer", "GraphNode", theme->get_icon(SNAME("GuiResizer"), SNAME("EditorIcons")));
	Ref<ImageTexture> port_icon = theme->get_icon(SNAME("GuiGraphNodePort"), SNAME("EditorIcons"));
	
	port_icon->set_size_override(Size2(12, 12));
	theme->set_icon("port", "GraphNode", port_icon);
	theme->set_font("title_font", "GraphNode", theme->get_font(SNAME("main_bold_msdf"), SNAME("EditorFonts")));
	
	theme->set_constant("v_separation", "GridContainer", Math::round(widget_default_margin.y - 2 * EDSCALE));
	
	theme->set_icon("folder", "FileDialog", theme->get_icon(SNAME("Folder"), SNAME("EditorIcons")));
	theme->set_icon("parent_folder", "FileDialog", theme->get_icon(SNAME("ArrowUp"), SNAME("EditorIcons")));
	theme->set_icon("back_folder", "FileDialog", theme->get_icon(SNAME("Back"), SNAME("EditorIcons")));
	theme->set_icon("forward_folder", "FileDialog", theme->get_icon(SNAME("Forward"), SNAME("EditorIcons")));
	theme->set_icon("reload", "FileDialog", theme->get_icon(SNAME("Reload"), SNAME("EditorIcons")));
	theme->set_icon("toggle_hidden", "FileDialog", theme->get_icon(SNAME("GuiVisibilityVisible"), SNAME("EditorIcons")));
	
	
	theme->set_color("folder_icon_color", "FileDialog", (dark_theme ? Color(1, 1, 1) : Color(4.25, 4.25, 4.25)).lerp(accent_color, 0.7));
	theme->set_color("files_disabled", "FileDialog", font_disabled_color);
	
	theme->set_constant("margin", "ColorPicker", default_margin_size);