### 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("#288027", "#218309"); 
	
	add_conversion_color_pair("#ffca5f", "#fea900"); 
	add_conversion_color_pair("#2998ff", "#68b6ff"); 
	add_conversion_color_pair("#a2d2ff", "#4998e3"); 
	add_conversion_color_pair("#69c4d4", "#29a3cc"); 
	
	
	add_conversion_color_pair("#ea7940", "#bd5e2c"); 
	add_conversion_color_pair("#ff2b88", "#bd165f"); 
	add_conversion_color_pair("#eac840", "#bd9d1f"); 
	add_conversion_color_pair("#3cf34e", "#16a827"); 
	add_conversion_color_pair("#2877f6", "#236be6"); 
	add_conversion_color_pair("#eae440", "#9f9722"); 
	add_conversion_color_pair("#a448f0", "#9853ce"); 
	add_conversion_color_pair("#5ad5c4", "#0a9c88"); 
	
	add_conversion_color_pair("#d6d6d6", "#474747"); 
	add_conversion_color_pair("#474747", "#d6d6d6"); 
	add_conversion_color_pair("#919191", "#6e6e6e"); 
	
	add_conversion_color_pair("#fce00e", "#aa8d24"); 
	add_conversion_color_pair("#0e71fc", "#0350bd"); 
	add_conversion_color_pair("#c6ced4", "#828f9b"); 
	
	add_conversion_color_pair("#41ecad", "#25e3a0"); 
	add_conversion_color_pair("#6f91f0", "#6d8eeb"); 
	add_conversion_color_pair("#5abbef", "#4fb2e9"); 
	add_conversion_color_pair("#35d4f4", "#27ccf0"); 
	add_conversion_color_pair("#4593ec", "#4690e7");