### 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
add_conversion_color_pair("#ee5677", "#ee7991"); 
	add_conversion_color_pair("#e0e0e0", "#5a5a5a"); 
	add_conversion_color_pair("#e1ec41", "#b2bb19"); 
	add_conversion_color_pair("#54ed9e", "#57e99f"); 
	add_conversion_color_pair("#417aec", "#6993ec"); 
	add_conversion_color_pair("#55f3e3", "#12d5c3"); 
	add_conversion_color_pair("#f74949", "#f77070"); 
	add_conversion_color_pair("#44bd44", "#46b946"); 
	add_conversion_color_pair("#ec418e", "#ec69a3"); 
	add_conversion_color_pair("#f1738f", "#ee758e"); 
	add_conversion_color_pair("#41ec80", "#2ce573"); 
	add_conversion_color_pair("#b9ec41", "#96ce1a"); 
	add_conversion_color_pair("#f68f45", "#f49047"); 
	add_conversion_color_pair("#ac73f1", "#ad76ee"); 
	add_conversion_color_pair("#de66f0", "#dc6aed"); 
	add_conversion_color_pair("#f066bd", "#ed6abd"); 
	
	add_conversion_color_pair("#77ce57", "#67c046"); 
	add_conversion_color_pair("#ea686c", "#d95256"); 
	add_conversion_color_pair("#eac968", "#d9b64f"); 
	add_conversion_color_pair("#cf68ea", "#c050dd"); 
	
	add_conversion_exception("EditorPivot");
	add_conversion_exception("EditorHandle");
	add_conversion_exception("Editor3DHandle");
	add_conversion_exception("EditorBoneHandle");
	add_conversion_exception("Godot");
	add_conversion_exception("Sky");
	add_conversion_exception("EditorControlAnchor");
	add_conversion_exception("DefaultProjectIcon");