### 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_stylebox("child_bg", "EditorProperty", style_property_child_bg);
	theme->set_constant("v_separation", "EditorProperty", (extra_spacing + default_margin_size) * EDSCALE);
	theme->set_color("warning_color", "EditorProperty", warning_color);
	theme->set_color("property_color", "EditorProperty", property_color);
	theme->set_color("readonly_color", "EditorProperty", readonly_color);
	theme->set_color("readonly_warning_color", "EditorProperty", readonly_warning_color);
	Ref<StyleBoxFlat> style_property_group_note = style_default->duplicate();
	Color property_group_note_color = accent_color;
	property_group_note_color.a = 0.1;
	style_property_group_note->set_bg_color(property_group_note_color);
	theme->set_stylebox("bg_group_note", "EditorProperty", style_property_group_note);
	
	Color inspector_section_color = font_color.lerp(Color(0.5, 0.5, 0.5), 0.35);
	theme->set_color("font_color", "EditorInspectorSection", inspector_section_color);
	Color inspector_indent_color = accent_color;
	inspector_indent_color.a = 0.2;
	Ref<StyleBoxFlat> inspector_indent_style = make_flat_stylebox(inspector_indent_color, 2.0 * EDSCALE, 0, 2.0 * EDSCALE, 0);
	theme->set_stylebox("indent_box", "EditorInspectorSection", inspector_indent_style);
	theme->set_constant("indent_size", "EditorInspectorSection", 6.0 * EDSCALE);
	theme->set_constant("inspector_margin", "Editor", 12 * EDSCALE);
	
	Ref<StyleBoxFlat> style_tree_bg = style_default->duplicate();
	
	style_tree_bg->set_bg_color(dark_color_1.lerp(dark_color_2, 0.5));
	if (draw_extra_borders) {
		style_tree_bg->set_border_width_all(Math::round(EDSCALE));
		style_tree_bg->set_border_color(extra_border_color_2);
	} else {
		style_tree_bg->set_border_color(dark_color_3);
	}