### 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
preset_base_color = Color(0.24, 0.26, 0.28);
		preset_contrast = default_contrast;
	} else if (preset == "Godot 2") {
		preset_accent_color = Color(0.53, 0.67, 0.89);
		preset_base_color = Color(0.24, 0.23, 0.27);
		preset_contrast = default_contrast;
	} else if (preset == "Gray") {
		preset_accent_color = Color(0.44, 0.73, 0.98);
		preset_base_color = Color(0.24, 0.24, 0.24);
		preset_contrast = default_contrast;
	} else if (preset == "Light") {
		preset_accent_color = Color(0.18, 0.50, 1.00);
		preset_base_color = Color(0.9, 0.9, 0.9);
		
		preset_contrast = -0.06;
	} else if (preset == "Solarized (Dark)") {
		preset_accent_color = Color(0.15, 0.55, 0.82);
		preset_base_color = Color(0.04, 0.23, 0.27);
		preset_contrast = default_contrast;
	} else if (preset == "Solarized (Light)") {
		preset_accent_color = Color(0.15, 0.55, 0.82);
		preset_base_color = Color(0.89, 0.86, 0.79);
		
		preset_contrast = -0.06;
	} else if (preset == "Black (OLED)") {
		preset_accent_color = Color(0.45, 0.75, 1.0);
		preset_base_color = Color(0, 0, 0);
		
		preset_contrast = 0.0;
		preset_draw_extra_borders = true;