### 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
const Color alpha3 = Color(mono_value, mono_value, mono_value, 0.27);
	const Color symbol_color = dark_theme ? Color(0.67, 0.79, 1) : Color(0, 0, 0.61);
	const Color keyword_color = dark_theme ? Color(1.0, 0.44, 0.52) : Color(0.9, 0.135, 0.51);
	const Color control_flow_keyword_color = dark_theme ? Color(1.0, 0.55, 0.8) : Color(0.743, 0.12, 0.8);
	const Color base_type_color = dark_theme ? Color(0.26, 1.0, 0.76) : Color(0, 0.6, 0.2);
	const Color engine_type_color = dark_theme ? Color(0.56, 1, 0.86) : Color(0.11, 0.55, 0.4);
	const Color user_type_color = dark_theme ? Color(0.78, 1, 0.93) : Color(0.18, 0.45, 0.4);
	const Color comment_color = dark_theme ? dim_color : Color(0.08, 0.08, 0.08, 0.5);
	const Color string_color = dark_theme ? Color(1, 0.93, 0.63) : Color(0.6, 0.42, 0);
	
	const Color te_background_color = dark_theme ? background_color : dark_color_3;
	const Color completion_background_color = dark_theme ? base_color : background_color;
	const Color completion_selected_color = alpha1;
	const Color completion_existing_color = alpha2;
	
	const Color completion_scroll_color = Color(mono_value, mono_value, mono_value, 0.29);
	const Color completion_scroll_hovered_color = Color(mono_value, mono_value, mono_value, 0.4);
	const Color completion_font_color = font_color;
	const Color text_color = font_color;
	const Color line_number_color = dim_color;
	const Color safe_line_number_color = dark_theme ? (dim_color * Color(1, 1.2, 1, 1.5)) : Color(0, 0.4, 0, 0.75);
	const Color caret_color = mono_color;
	const Color caret_background_color = mono_color.inverted();
	const Color text_selected_color = Color(0, 0, 0, 0);
	const Color brace_mismatch_color = dark_theme ? error_color : Color(1, 0.08, 0, 1);
	const Color current_line_color = alpha1;
	const Color line_length_guideline_color = dark_theme ? base_color : background_color;
	const Color word_highlighted_color = alpha1;
	const Color number_color = dark_theme ? Color(0.63, 1, 0.88) : Color(0, 0.55, 0.28, 1);
	const Color function_color = dark_theme ? Color(0.34, 0.7, 1.0) : Color(0, 0.225, 0.9, 1);